class_docstr: Abstract base class for version numbering classes.  Just provides
  constructor (__init__) and reproducer (__repr__), because those
  seem to be the same for all version numbering classes; and route
  rich comparisons to _cmp.
code: def __repr__(self):
      return "{} ('{}')".format(self.__class__.__name__, str(self))
  
imports: import re
  import warnings
  import contextlib
label_desc: Use image node_id 2 for calling the Version obj's underlying member method code with example usage: obj.__repr__() and returns: str