docs: def decamel_to_snake(string):
      """Convert to lower case, join camel case with underscore.
      CamelCase -> camel_case. Camel Case -> camel_case.
      """
      strings = [decamel(word) if not word.isupper() else word.lower()
                 for word in string.split()]
      return "_".join([snake(dstring)for dstring in strings])