def get_index(self, name, *args):
    if ((len(args) == 0) or (name not in self.indices)):
        return None
    index = self.indices[name]
    result = index[args[0]]
    for key in args[1:]:
        result = result.intersection(index[key])
    return result
def get_index(self, name, *args):
    if ((len(args) == 0) or (name not in self.indices)):
        return None
    index = self.indices[name]
    result = index[args[0]]
    for key in args[1:]:
        result = result.intersection(index[key])
    return result