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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_gene_onto(pdb_id):
 """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 -------- {'@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'}} """

    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