Add report numbers.

        :param report_number: report number for the current document
        :type report_number: string

        :param source: source for the given report number
        :type source: string

def add_report_number(self, report_number, source=None):
        """Add report numbers.

        :param report_number: report number for the current document
        :type report_number: string

        :param source: source for the given report number
        :type source: string
        """
        self._append_to('report_numbers', self._sourced_dict(
            source,
            value=report_number,
        ))