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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def from_response(cls, response_data):
 """ Factory method to create a Mail instance from a Guerrillamail response dict. """

        identity = lambda x: x
        return Mail(**_transform_dict(response_data, {
            'guid': ('mail_id', identity),
            'subject': ('mail_subject', identity),
            'sender': ('mail_from', identity),
            'datetime': ('mail_timestamp', lambda x: datetime.utcfromtimestamp(int(x)).replace(tzinfo=utc)),
            'read': ('mail_read', int),
            'excerpt': ('mail_excerpt', identity),
            'body': ('mail_body', identity),
        }))