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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_discovery_doc(self, services, hostname=None):
 """JSON dict description of a protorpc.remote.Service in discovery format. Args: services: Either a single protorpc.remote.Service or a list of them that implements an api/version. hostname: string, Hostname of the API, to override the value set on the current service. Defaults to None. Returns: dict, The discovery document as a JSON dict. """


    if not isinstance(services, (tuple, list)):
      services = [services]

    # The type of a class that inherits from remote.Service is actually
    # remote._ServiceClass, thanks to metaclass strangeness.
    # pylint: disable=protected-access
    util.check_list_type(services, remote._ServiceClass, 'services',
                         allow_none=False)

    return self.__discovery_doc_descriptor(services, hostname=hostname)