@staticmethod
def _map_descriptor(mapper):
    """Prepare part one of the dsc file data for adding to the metadata.

        Parameters
        ----------
        mapper : :obj:`aspecd.metadata.MetadataMapper`
            metadata mapper containing the respective first part of the
            dsc file as metadata.
        """
    mapper.mappings = [['Data Ranges and Resolutions:', 'rename_key', [
        'XPTS', 'step_count']], ['Data Ranges and Resolutions:',
        'rename_key', ['XMIN', 'field_min']], [
        'Data Ranges and Resolutions:', 'rename_key', ['XWID',
        'field_width']], ['', 'rename_key', ['Data Ranges and Resolutions:',
        'magnetic_field']]]
    mapper.map()
    return mapper.metadata
