docs: def expect_err(self, msg) -> E:
          """
          Returns the error value in a :class:`Result`, or raises a
          ``ValueError`` with the provided message.
  
          Args:
              msg: The error message.
  
          Returns:
              The error value in the :class:`Result` if it is a
              :meth:`Result.Err` value.
  
          Raises:
              ``ValueError`` with the message provided by ``msg`` if
              the :class:`Result` is a :meth:`Result.Ok` value.
  
          Examples:
              >>> try:
              ...     Ok(1).expect_err('Oh No')
              ... except ValueError as e:
              ...     print(e)
              Oh No
              >>> Err(1).expect_err('Yes')
              1
          """
          if self._is_ok:
              raise ValueError(msg)
          return cast(E, self._val)