docs: def find_version(filename):
      """
      Search for assignment of __version__ string in given file and
      return what it is assigned to.
      """
      with open(filename, "r") as filep:
          version_file = filep.read()
          version_match = re.search(
              r"^__version__ = ['\"]([^'\"]*)['\"]", version_file, re.M
          )
          if version_match:
              return version_match.group(1)
          raise RuntimeError("Unable to find version string.")