Given a structure or structure entry identifer (e.g. PDB:1crn), return the structure in PDB format. If a structure identifier, in database:identifier format, is input the EBI's WSDbfetch web service (see http://www.ebi.ac.uk/Tools/webservices/services/dbfetch) is used to retrive the structure in PDB format. Otherwise the input is assumed to be a formated structure and is passed through to the output.