@classmethod
def _convert_postmark_to_native(cls, message):
    """Converts Postmark message API field names to their corresponding
        :class:`Message` attribute names.

        :param message: Postmark message data, with API fields using Postmark
            API names.
        :type message: `dict`
        """
    d = {}
    for dest, src in cls._fields.items():
        if src in message:
            d[dest] = message[src]
    return d
