refactor(modpathfile): step toward generic particle tracking api

* introduce particletracking module and ParticleTrackFile base class
* rename _ModpathSeries -> ModpathFile
* deduplicate shared logic in ModpathFile
* add dtypes as public class attributes
* clarify canonical (minimal) fields
* prep to support PRT output files

autotest/test_modpathfile.py

@@ -347,7 +347,7 @@ def test_write_shapefile(function_tmpdir, mp7_small, longfieldname):
 
     # write the pathline recarray to shapefile
     pathline_file.write_shapefile(
-        pathline_data=pathlines,
+        data=pathlines,
         shpname=shp_file,
         one_per_particle=False,
         mg=grid,

autotest/test_mp5.py

@@ -1,10 +1,8 @@
 import os
 
 import numpy as np
-import pandas as pd
 from autotest.test_mp6 import eval_timeseries
 from matplotlib import pyplot as plt
-from modflow_devtools.markers import requires_pkg
 
 from flopy.modflow import Modflow
 from flopy.plot import PlotMapView
@@ -50,14 +48,8 @@ def test_mp5_load(function_tmpdir, example_data_path):
     for n in pthobj.nid:
         p = pthobj.get_data(partid=n)
         e = endobj.get_data(partid=n)
-        try:
-            mm.plot_pathline(p, colors=colors[n], layer="all")
-        except:
-            assert False, f'could not plot pathline {n + 1} with layer="all"'
-        try:
-            mm.plot_endpoint(e)
-        except:
-            assert False, f'could not plot endpoint {n + 1} with layer="all"'
+        mm.plot_pathline(p, colors=colors[n], layer="all")
+        mm.plot_endpoint(e)
 
     # plot the grid and ibound array
     mm.plot_grid(lw=0.5)

flopy/utils/flopy_io.py

@@ -352,7 +352,6 @@ def loadtxt(
     ra : np.recarray
         Numpy record array of file contents.
     """
-    from ..utils import import_optional_dependency
 
     if use_pandas:
         if delimiter.isspace():