code: def read(self):
          # type: () -> Optional[str]
          
          with open(self.version_file) as fp:
              version = fp.read().strip()
  
              if is_valid(version):
                  return version
  
              return None
docs: Read the project version from .py file.
  
          This will regex search in the file for a
          ``__version__ = VERSION_STRING`` and read the version string.