code: def get_gene_onto(pdb_id):
      
      out = get_info(pdb_id, url_root = 'http://www.rcsb.org/pdb/rest/goTerms?structureId=')
      out = to_dict(out)
      if not out['goTerms']:
          return None
      out = remove_at_sign(out['goTerms'])
      return out
docs: Return ligands of given PDB_ID
  
      Parameters
      ----------
  
      pdb_id : string
          A 4 character string giving a pdb entry of interest
  
      Returns
      -------
  
      out : dict
          A dictionary containing the gene ontology information associated with the entry
  
      Examples
      --------
  
      >>> gene_info = get_gene_onto('4Z0L')
      >>> print(gene_info['term'][0])
      {'@chainId': 'A',
       '@id': 'GO:0001516',
       '@structureId': '4Z0L',
       'detail': {'@definition': 'The chemical reactions and pathways resulting '
                                 'in the formation of prostaglandins, any of a '
                                 'group of biologically active metabolites which '
                                 'contain a cyclopentane ring.',
                  '@name': 'prostaglandin biosynthetic process',
                  '@ontology': 'B',
                  '@synonyms': 'prostaglandin anabolism, prostaglandin '
                               'biosynthesis, prostaglandin formation, '
                               'prostaglandin synthesis'}}