code: def _egg_info_matches(egg_info, canonical_name):
      # type: (str, str) -> Optional[str]
      
      try:
          version_start = _find_name_version_sep(egg_info, canonical_name) + 1
      except ValueError:
          return None
      version = egg_info[version_start:]
      if not version:
          return None
      return version
docs: Pull the version part out of a string.
  
      :param egg_info: The string to parse. E.g. foo-2.1
      :param canonical_name: The canonicalized name of the package this
          belongs to.