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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 to_mllp(self, encoding_chars=None, trailing_children=False):
 """ Returns the er7 representation of the message wrapped with mllp encoding characters :type encoding_chars: ``dict`` :param encoding_chars: a dictionary containing the encoding chars or None to use the default (see :func:`get_default_encoding_chars <hl7apy.get_default_encoding_chars>`) :type trailing_children: ``bool`` :param trailing_children: if ``True``, trailing children will be added even if their value is ``None`` :return: the ER7-encoded string wrapped with the mllp encoding characters """

        if encoding_chars is None:
            encoding_chars = self.encoding_chars

        return "{0}{1}{2}{3}{2}".format(MLLP_ENCODING_CHARS.SB,
                                        self.to_er7(encoding_chars, trailing_children),
                                        MLLP_ENCODING_CHARS.CR,
                                        MLLP_ENCODING_CHARS.EB)