diff --git a/plotille/_cmaps.py b/plotille/_cmaps.py
index c4d2f8b..284d531 100644
--- a/plotille/_cmaps.py
+++ b/plotille/_cmaps.py
@@ -38,7 +38,7 @@ class Colormap(object):
     Colormap represents. Scaling the data into the `[0, 1]` interval is
     responsibility of the caller.
     """
-    def __init__(self, name):
+    def __init__(self, name, lookup_table=None):
         """
         Parameters
         ----------
@@ -48,7 +48,7 @@ def __init__(self, name):
             The number of rgb quantization levels.
         """
         self.name = name
-        self._lookup_table = None
+        self._lookup_table = lookup_table
         self.bad = None
         self.over = None
         self.under = None
@@ -86,8 +86,7 @@ def _process_value(self, x):
 
 class ListedColormap(Colormap):
     def __init__(self, name, colors):
-        super(ListedColormap, self).__init__(name)
-        self._lookup_table = colors
+        super(ListedColormap, self).__init__(name, lookup_table=colors)
 
     @classmethod
     def from_relative(cls, name, colors):
diff --git a/plotille/_figure.py b/plotille/_figure.py
index ee1fc9b..43725b4 100644
--- a/plotille/_figure.py
+++ b/plotille/_figure.py
@@ -31,7 +31,7 @@
 from ._colors import color, rgb2byte
 from ._figure_data import Heat, Histogram, Plot, Span, Text
 from ._input_formatter import InputFormatter
-from ._util import mk_timedelta, timestamp
+from ._util import mk_timedelta
 
 # TODO documentation!!!
 # TODO tests
@@ -244,7 +244,7 @@ def _limits(self, low_set, high_set, is_height):
     def _y_axis(self, ymin, ymax, label='Y'):
         delta = abs(ymax - ymin)
         if isinstance(delta, timedelta):
-            y_delta = mk_timedelta(timestamp(delta) / self.height)
+            y_delta = mk_timedelta(delta.total_seconds() / self.height)
         else:
             y_delta = delta / self.height
 
@@ -271,7 +271,7 @@ def _y_axis(self, ymin, ymax, label='Y'):
     def _x_axis(self, xmin, xmax, label='X', with_y_axis=False):
         delta = abs(xmax - xmin)
         if isinstance(delta, timedelta):
-            x_delta = mk_timedelta(timestamp(delta) / self.width)
+            x_delta = mk_timedelta(delta.total_seconds() / self.width)
         else:
             x_delta = delta / self.width
         starts = ['', '']
@@ -546,7 +546,7 @@ def _diff(low, high):
     else:
         delta = abs(high - low)
         if isinstance(delta, timedelta):
-            return mk_timedelta(timestamp(delta) * 0.1)
+            return mk_timedelta(delta.total_seconds() * 0.1)
         else:
             return delta * 0.1
 
@@ -568,6 +568,7 @@ def _default(low_set, high_set):
             return low_set, 1.0
 
     # Should never get here! => checked in function before
+    raise ValueError('Unexpected inputs!')
 
 
 def _choose(low, high, low_set, high_set):
@@ -600,3 +601,4 @@ def _choose(low, high, low_set, high_set):
             return low_set, high + diff
 
         # Should never get here! => checked in function before
+        raise ValueError('Unexpected inputs!')
diff --git a/plotille/_input_formatter.py b/plotille/_input_formatter.py
index 3e2fdb6..5660a15 100644
--- a/plotille/_input_formatter.py
+++ b/plotille/_input_formatter.py
@@ -27,7 +27,7 @@
 from datetime import date, datetime, time, timedelta
 import math
 
-from ._util import roundeven, timestamp
+from ._util import roundeven
 
 
 class InputFormatter(object):
@@ -138,6 +138,7 @@ def _num_formatter(val, chars, delta, left=False):
         return _int_formatter(val, chars, left)
     elif isinstance(val, float):
         return _float_formatter(val, chars, left)
+    # unreachable
 
 
 def _float_formatter(val, chars, left=False):
@@ -206,7 +207,7 @@ def _convert_numbers(v):
 
 def _convert_np_datetime(v):
     # assert isinstance(v, np.datetime64)
-    return timestamp(v.item())
+    return v.item().timestamp()
 
 
 def _convert_date(v):
@@ -216,4 +217,4 @@ def _convert_date(v):
 
 def _convert_datetime(v):
     assert isinstance(v, datetime)
-    return timestamp(v)
+    return v.timestamp()
diff --git a/plotille/_util.py b/plotille/_util.py
index 21a12a1..458df21 100644
--- a/plotille/_util.py
+++ b/plotille/_util.py
@@ -23,9 +23,8 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-from datetime import datetime, timedelta, tzinfo
+from datetime import timedelta, tzinfo
 import math
-import time
 
 
 def roundeven(x):
@@ -78,7 +77,7 @@ def hist(X, bins):
     is_datetime = False
     if isinstance(delta, timedelta):
         is_datetime = True
-        delta = timestamp(delta)
+        delta = delta.total_seconds()
 
     xwidth = delta / bins
 
@@ -87,7 +86,7 @@ def hist(X, bins):
         x_ = _numpy_to_native(x)
         delta = (x_ - xmin)
         if isinstance(delta, timedelta):
-            delta = timestamp(delta)
+            delta = delta.total_seconds()
         x_idx = min(bins - 1, int(delta // xwidth))
         y[x_idx] += 1
 
@@ -111,20 +110,6 @@ def dst(self, dt):
         return self._ZERO
 
 
-_EPOCH = datetime(1970, 1, 1, tzinfo=_UTC())
-
-
-def timestamp(v):
-    """Get timestamp of `v` datetime in py2/3."""
-    if isinstance(v, datetime):
-        if v.tzinfo is None:
-            return time.mktime(v.timetuple()) + v.microsecond / 1e6
-        else:
-            return (v - _EPOCH).total_seconds()
-    elif isinstance(v, timedelta):
-        return v.total_seconds()
-
-
 def mk_timedelta(v):
     seconds = int(v)
     microseconds = int((v - seconds) * 1e6)
diff --git a/poetry.lock b/poetry.lock
index 39feea5..fb6bafe 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -15,10 +15,10 @@ optional = false
 python-versions = ">=3.5"
 
 [package.extras]
-dev = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "zope.interface", "furo", "sphinx", "sphinx-notfound-page", "pre-commit", "cloudpickle"]
-docs = ["furo", "sphinx", "zope.interface", "sphinx-notfound-page"]
-tests = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "zope.interface", "cloudpickle"]
-tests_no_zope = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "cloudpickle"]
+dev = ["cloudpickle", "coverage[toml] (>=5.0.2)", "furo", "hypothesis", "mypy (>=0.900,!=0.940)", "pre-commit", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "sphinx", "sphinx-notfound-page", "zope.interface"]
+docs = ["furo", "sphinx", "sphinx-notfound-page", "zope.interface"]
+tests = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy (>=0.900,!=0.940)", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "zope.interface"]
+tests-no-zope = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy (>=0.900,!=0.940)", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins"]
 
 [[package]]
 name = "colorama"
@@ -69,7 +69,7 @@ attrs = ">=19.2.0"
 flake8 = ">=3.0.0"
 
 [package.extras]
-dev = ["tox", "coverage", "hypothesis", "hypothesmith (>=0.2)", "pre-commit"]
+dev = ["coverage", "hypothesis", "hypothesmith (>=0.2)", "pre-commit", "tox"]
 
 [[package]]
 name = "flake8-commas"
@@ -104,6 +104,7 @@ python-versions = "*"
 
 [package.dependencies]
 pycodestyle = "*"
+setuptools = "*"
 
 [[package]]
 name = "flake8-pep3101"
@@ -154,8 +155,8 @@ typing-extensions = {version = ">=3.6.4", markers = "python_version < \"3.8\""}
 zipp = ">=0.5"
 
 [package.extras]
-docs = ["sphinx", "jaraco.packaging (>=8.2)", "rst.linker (>=1.9)"]
-testing = ["pytest (>=4.6)", "pytest-checkdocs (>=2.4)", "pytest-flake8", "pytest-cov", "pytest-enabler (>=1.0.1)", "packaging", "pep517", "pyfakefs", "flufl.flake8", "pytest-black (>=0.3.7)", "pytest-mypy", "importlib-resources (>=1.3)"]
+docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
+testing = ["flufl.flake8", "importlib-resources (>=1.3)", "packaging", "pep517", "pyfakefs", "pytest (>=4.6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.0.1)", "pytest-flake8", "pytest-mypy"]
 
 [[package]]
 name = "iniconfig"
@@ -185,7 +186,7 @@ python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 six = "*"
 
 [package.extras]
-build = ["twine", "wheel", "blurb"]
+build = ["blurb", "twine", "wheel"]
 docs = ["sphinx"]
 test = ["pytest", "pytest-cov"]
 
@@ -299,7 +300,7 @@ optional = false
 python-versions = ">=3.6.8"
 
 [package.extras]
-diagrams = ["railroad-diagrams", "jinja2"]
+diagrams = ["jinja2", "railroad-diagrams"]
 
 [[package]]
 name = "pytest"
@@ -336,7 +337,7 @@ coverage = {version = ">=5.2.1", extras = ["toml"]}
 pytest = ">=4.6"
 
 [package.extras]
-testing = ["fields", "hunter", "process-tests", "six", "pytest-xdist", "virtualenv"]
+testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtualenv"]
 
 [[package]]
 name = "pytest-mock"
@@ -382,6 +383,19 @@ category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 
+[[package]]
+name = "setuptools"
+version = "65.6.3"
+description = "Easily download, build, install, upgrade, and uninstall Python packages"
+category = "dev"
+optional = false
+python-versions = ">=3.7"
+
+[package.extras]
+docs = ["furo", "jaraco.packaging (>=9)", "jaraco.tidelift (>=1.4)", "pygments-github-lexers (==0.0.5)", "rst.linker (>=1.9)", "sphinx (>=3.5)", "sphinx-favicon", "sphinx-hoverxref (<2)", "sphinx-inline-tabs", "sphinx-notfound-page (==0.8.3)", "sphinx-reredirects", "sphinxcontrib-towncrier"]
+testing = ["build[virtualenv]", "filelock (>=3.4.0)", "flake8 (<5)", "flake8-2020", "ini2toml[lite] (>=0.9)", "jaraco.envs (>=2.2)", "jaraco.path (>=3.2.0)", "pip (>=19.1)", "pip-run (>=8.8)", "pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.3)", "pytest-flake8", "pytest-mypy (>=0.9.1)", "pytest-perf", "pytest-timeout", "pytest-xdist", "tomli-w (>=1.0.0)", "virtualenv (>=13.0.0)", "wheel"]
+testing-integration = ["build[virtualenv]", "filelock (>=3.4.0)", "jaraco.envs (>=2.2)", "jaraco.path (>=3.2.0)", "pytest", "pytest-enabler", "pytest-xdist", "tomli", "virtualenv (>=13.0.0)", "wheel"]
+
 [[package]]
 name = "six"
 version = "1.16.0"
@@ -423,8 +437,8 @@ optional = false
 python-versions = ">=3.7"
 
 [package.extras]
-docs = ["sphinx (>=3.5)", "jaraco.packaging (>=9)", "rst.linker (>=1.9)", "furo", "jaraco.tidelift (>=1.4)"]
-testing = ["pytest (>=6)", "pytest-checkdocs (>=2.4)", "flake8 (<5)", "pytest-cov", "pytest-enabler (>=1.3)", "jaraco.itertools", "func-timeout", "jaraco.functools", "more-itertools", "pytest-black (>=0.3.7)", "pytest-mypy (>=0.9.1)", "pytest-flake8"]
+docs = ["furo", "jaraco.packaging (>=9)", "jaraco.tidelift (>=1.4)", "rst.linker (>=1.9)", "sphinx (>=3.5)"]
+testing = ["flake8 (<5)", "func-timeout", "jaraco.functools", "jaraco.itertools", "more-itertools", "pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.3)", "pytest-flake8", "pytest-mypy (>=0.9.1)"]
 
 [metadata]
 lock-version = "1.1"
@@ -741,6 +755,10 @@ pytzdata = [
     {file = "pytzdata-2020.1-py2.py3-none-any.whl", hash = "sha256:e1e14750bcf95016381e4d472bad004eef710f2d6417240904070b3d6654485f"},
     {file = "pytzdata-2020.1.tar.gz", hash = "sha256:3efa13b335a00a8de1d345ae41ec78dd11c9f8807f522d39850f2dd828681540"},
 ]
+setuptools = [
+    {file = "setuptools-65.6.3-py3-none-any.whl", hash = "sha256:57f6f22bde4e042978bcd50176fdb381d7c21a9efa4041202288d3737a0c6a54"},
+    {file = "setuptools-65.6.3.tar.gz", hash = "sha256:a7620757bf984b58deaf32fc8a4577a9bbc0850cf92c20e1ce41c38c19e5fb75"},
+]
 six = [
     {file = "six-1.16.0-py2.py3-none-any.whl", hash = "sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254"},
     {file = "six-1.16.0.tar.gz", hash = "sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926"},
diff --git a/tests/test_data.py b/tests/test_data.py
index 0f1114b..8ab0e3a 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -66,7 +66,7 @@ def test_circle(radius):
     assert Y[0] == pytest.approx(Y[-1], abs=0.001)
 
     for x, y in zip(X, Y):
-        assert math.sqrt(x**2 + y**2) == pytest.approx(radius**10, abs=0.001)
+        assert math.hypot(x, y) == pytest.approx(radius**10, abs=0.001)
         equal = 0
         for x2, y2 in zip(X, Y):
             if x2 == x and y2 == y:
diff --git a/tests/test_examples.py b/tests/test_examples.py
index 735eca0..5aad453 100644
--- a/tests/test_examples.py
+++ b/tests/test_examples.py
@@ -7,19 +7,6 @@
 
 import pytest
 
-try:
-    import numpy  # noqa: F401
-    have_numpy = True
-except ImportError:
-    have_numpy = False
-
-
-try:
-    from PIL import Image  # noqa: F401
-    have_pillow = True
-except ImportError:
-    have_pillow = False
-
 
 @pytest.fixture
 def change_to_examples_dir(request):
@@ -28,8 +15,6 @@ def change_to_examples_dir(request):
     os.chdir(str(request.config.invocation_dir))
 
 
-@pytest.mark.skipif(not have_numpy, reason='No numpy installed.')
-@pytest.mark.skipif(not have_pillow, reason='No pillow installed.')
 def test_examples(change_to_examples_dir):
     sys.path.insert(0, '.')
     for fname in glob('*_example.py'):