How to use the nanopb.nanopb.generator.nanopb_generator.Globals.separate_options function in nanopb

paths = ['.'] + options.options_path
    for p in paths:
        if os.path.isfile(os.path.join(p, optfilename)):
            optfilename = os.path.join(p, optfilename)
            if options.verbose:
                sys.stderr.write('Reading options from ' + optfilename + '\n')
            Globals.separate_options = read_options_file(open(optfilename, "rU"))
            break
    else:
        # If we are given a full filename and it does not exist, give an error.
        # However, don't give error when we automatically look for .options file
        # with the same name as .proto.
        if options.verbose or had_abspath:
            sys.stderr.write('Options file not found: ' + optfilename + '\n')
        Globals.separate_options = []

    Globals.matched_namemasks = set()

    # Parse the file
    file_options = get_nanopb_suboptions(fdesc, toplevel_options, Names([filename]))
    f = ProtoFile(fdesc, file_options)
    f.optfilename = optfilename

    return f

def get_nanopb_suboptions(subdesc, options, name):
    '''Get copy of options, and merge information from subdesc.'''
    new_options = nanopb_pb2.NanoPBOptions()
    new_options.CopyFrom(options)

    if hasattr(subdesc, 'syntax') and subdesc.syntax == "proto3":
        new_options.proto3 = True

    # Handle options defined in a separate file
    dotname = '.'.join(name.parts)
    for namemask, options in Globals.separate_options:
        if fnmatch(dotname, namemask):
            Globals.matched_namemasks.add(namemask)
            new_options.MergeFrom(options)

    # Handle options defined in .proto
    if isinstance(subdesc.options, descriptor.FieldOptions):
        ext_type = nanopb_pb2.nanopb
    elif isinstance(subdesc.options, descriptor.FileOptions):
        ext_type = nanopb_pb2.nanopb_fileopt
    elif isinstance(subdesc.options, descriptor.MessageOptions):
        ext_type = nanopb_pb2.nanopb_msgopt
    elif isinstance(subdesc.options, descriptor.EnumOptions):
        ext_type = nanopb_pb2.nanopb_enumopt
    else:
        raise Exception("Unknown options type")