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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 attach_related(self, filename=None, content=None, mimetype=None):
 """ Attaches a file with the given filename and content. The filename can be omitted and the mimetype is guessed, if not provided. If the first parameter is a MIMEBase subclass it is inserted directly into the resulting message attachments. """

        if isinstance(filename, MIMEBase):
            assert content == mimetype == None
            self.related_attachments.append(filename)
        else:
            assert content is not None
            self.related_attachments.append((filename, content, mimetype))