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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 get_attachment_content(self, ticket_id, attachment_id):
 """ Get content of attachment without headers. This function is necessary to use for binary attachment, as it can contain ``\\n`` chars, which would disrupt parsing of message if :py:meth:`~Rt.get_attachment` is used. Format of message:: :param ticket_id: ID of ticket :param attachment_id: ID of attachment Returns: Bytes with content of attachment or None if ticket or attachment does not exist. """


        msg = self.__request('ticket/{}/attachments/{}/content'.format
                             (str(ticket_id), str(attachment_id)),
                             text_response=False)
        lines = msg.split(b'\n', 3)
        if (len(lines) == 4) and (self.RE_PATTERNS['invalid_attachment_pattern_bytes'].match(lines[2]) or self.RE_PATTERNS['does_not_exist_pattern_bytes'].match(lines[2])):
            return None
        return msg[msg.find(b'\n') + 2:-3]