modify the Dumper subclass state instead of the global yaml state. na…

…tcap#49

src/geometamaker/utils.py

@@ -1,28 +1,29 @@
 import yaml
 
 
-def represent_str(dumper, data):
+def _represent_str(dumper, data):
     scalar = yaml.representer.SafeRepresenter.represent_str(dumper, data)
     if len(data.splitlines()) > 1:
         scalar.style = '|'  # literal style, newline chars will be new lines
     return scalar
 
 
-# Patch the default string representer so that it uses
-# a literal block style when the data contain newline characters
-yaml.SafeDumper.add_representer(str, represent_str)
+class _SafeDumper(yaml.SafeDumper):
 
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        # Patch the default string representer to use a literal block
+        # style when the data contain newline characters
+        self.add_representer(str, _represent_str)
 
-# https://stackoverflow.com/questions/13518819/avoid-references-in-pyyaml
-class _NoAliasDumper(yaml.SafeDumper):
-    """Keep the yaml human-readable by avoiding anchors and aliases."""
-
+    # https://stackoverflow.com/questions/13518819/avoid-references-in-pyyaml
     def ignore_aliases(self, data):
+        """Keep the yaml human-readable by avoiding anchors and aliases."""
         return True
 
 
 def yaml_dump(data):
     return yaml.dump(
         data,
         allow_unicode=True,
-        Dumper=_NoAliasDumper)
+        Dumper=_SafeDumper)