How to use the blinker._utilities.defaultdict function in blinker

def __init__(self, doc=None):
        """
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

... versionadded:: 1.5
        """
        if doc:
            self.__doc__ = doc
        if receiver_adapter is not Unspecified:
            self.receiver_adapter = receiver_adapter
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

def __init__(self, doc=None):
        """
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

def _by_receiver(self):
        return self.local.__dict__.setdefault("_by_receiver", defaultdict(set))

"""
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

"""
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

def __init__(self, doc=None):
        """
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

def __init__(self, doc=None):
        """
        :param doc: optional.  If provided, will be assigned to the signal's
          __doc__ attribute.

        """
        if doc:
            self.__doc__ = doc
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}

def _by_sender(self):
        return self.local.__dict__.setdefault("_by_sender", defaultdict(set))

:meth:`send` instead of invoking receivers functions directly.

        ... versionadded:: 1.5
        """
        if doc:
            self.__doc__ = doc
        if receiver_adapter is not Unspecified:
            self.receiver_adapter = receiver_adapter
        #: A mapping of connected receivers.
        #:
        #: The values of this mapping are not meaningful outside of the
        #: internal :class:`Signal` implementation, however the boolean value
        #: of the mapping is useful as an extremely efficient check to see if
        #: any receivers are connected to the signal.
        self.receivers = {}
        self._by_receiver = defaultdict(set)
        self._by_sender = defaultdict(set)
        self._weak_senders = {}