code: protected static void copyLigandsByProximity(Structure full, Structure reduced) {
  		// Normal case where all models should be copied from full to reduced
  		assert full.nrModels() >= reduced.nrModels();
  		for(int model = 0; model< reduced.nrModels(); model++) {
  			copyLigandsByProximity(full, reduced, StructureTools.DEFAULT_LIGAND_PROXIMITY_CUTOFF, model, model);
  		}
  	}
docs: Supplements the reduced structure with ligands from the full structure based on
  a distance cutoff. Ligand groups are moved (destructively) from full to reduced
  if they fall within the cutoff of any atom in the reduced structure.
  The {@link StructureTools#DEFAULT_LIGAND_PROXIMITY_CUTOFF default cutoff}
  is used.
  @param full Structure containing all ligands
  @param reduced Structure with a subset of the polymer groups from full
  @see StructureTools#getLigandsByProximity(java.util.Collection, Atom[], double)