<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def load_go_graph(go_fname):
 """Load the GO data from an OWL file and parse into an RDF graph. Parameters go_fname : str Path to the GO OWL file. Can be downloaded from http://geneontology.org/ontology/go.owl. Returns ------- rdflib.Graph RDF graph containing GO data. """

    global _go_graph
    if _go_graph is None:
        _go_graph = rdflib.Graph()
        logger.info("Parsing GO OWL file")
        _go_graph.parse(os.path.abspath(go_fname))
    return _go_graph