code: @Override
  	public Structure loadStructure(AtomCache cache) throws IOException, StructureException {
  		String pdb = getPdbId();
  		if(pdb == null)
  			return null;
  		return cache.getStructureForPdbId(pdb);
  	}
docs: Loads the complete structure based on {@link #getPdbId()}.
  
  @param AtomCache A source of structures
  @return A Structure containing at least the atoms identified by this,
  or null if no PDB ID is set
  @throws StructureException For errors loading and parsing the structure
  @throws IOException Errors reading the structure from disk