Data items in the IHM_LOCALIZATION_DENSITY_FILES category records the
               details of files that provide information regarding localization densities
               of ensembles. These may be stored externally as local files or linked via 
               DOI and can be in any accepted format that provides volume information 
               (CCP4, MRC, etc.).
 
    loop_
    _ihm_localization_density_files.id
    _ihm_localization_density_files.file_id
    _ihm_localization_density_files.ensemble_id
    _ihm_localization_density_files.entity_id
    _ihm_localization_density_files.asym_id
    _ihm_localization_density_files.entity_poly_segment_id
    1 12 1 1 A 1 
    2 13 1 2 B 2 
    3 14 1 3 C 3 
    # ...abbreviated...