Build the data block of :class:`~ctfile.ctfile.SDfile` instance. 

        :return: Data block.
        :rtype: :py:class:`collections.OrderedDict`.

def _build_data_block(self, lexer):
        """Build the data block of :class:`~ctfile.ctfile.SDfile` instance. 

        :return: Data block.
        :rtype: :py:class:`collections.OrderedDict`.
        """
        data_block = OrderedDict()
        header = ''

        while True:
            token = next(lexer)
            key = token.__class__.__name__

            if key == 'DataHeader':
                header = token.header[1:-1]
                data_block.setdefault(header, [])

            elif key == 'DataItem':
                data_block[header].append(token.data_item)

            elif key == 'DataBlockEnd':
                break

            else:
                raise KeyError('SDfile data block does not supposed to have any other information: "{}".'.format(key))

        return data_block