def get_write_fields(self):
        """
        Get the list of fields used to write the multi-segment header.
        Returns the default required fields, the user defined fields,
        and their dependencies.

        """

        # Record specification fields
        write_fields = self.get_write_subset('record')

        # Segment specification fields are all mandatory
        write_fields = write_fields + ['seg_name', 'seg_len']

        # Comments
        if self.comments !=None:
            write_fields.append('comments')
        return write_fields
Get the list of fields used to write the multi-segment header.
        Returns the default required fields, the user defined fields,
        and their dependencies.