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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 _prepare_body(self):
 """ private function to prepare content for paramType=body """

        content_type = self.__consume
        if not content_type:
            content_type = self.__op.consumes[0] if self.__op.consumes else 'application/json'
        if self.__op.consumes and content_type not in self.__op.consumes:
            raise errs.SchemaError('content type {0} does not present in {1}'.format(content_type, self.__op.consumes))

        # according to spec, payload should be one and only,
        # so we just return the first value in dict.
        for parameter in self.__op.parameters:
            parameter = final(parameter)
            if getattr(parameter, 'in') == 'body':
                schema = deref(parameter.schema)
                _type = schema.type
                _format = schema.format
                name = schema.name
                body = self.__p['body'][parameter.name]
                return content_type, self.__op._mime_codec.marshal(content_type, body, _type=_type, _format=_format, name=name)
        return None, None