bidict: global name 'BidirectionalMapping' is not defined

Hi, we are using version bidict==0.18.0 and CPython 2.7.13 and got the following error here:

bidict/_abc.py in subclasshook at line 90

    def __subclasshook__(cls, C):  # noqa: N803 (argument name should be lowercase)
        """Check if *C* is a :class:`~collections.abc.Mapping`
        that also provides an ``inverse`` attribute,
        thus conforming to the :class:`BidirectionalMapping` interface,
        in which case it will be considered a (virtual) C
        even if it doesn't explicitly extend it.
        """
        that also provides an ``inverse`` attribute,
        thus conforming to the :class:`BidirectionalMapping` interface,
        in which case it will be considered a (virtual) C
        even if it doesn't explicitly extend it.
        """
        if cls is not BidirectionalMapping:  # lgtm [py/comparison-using-is]  # global name 'BidirectionalMapping' is not defined here
            return NotImplemented
        if not Mapping.__subclasshook__(C):
            return NotImplemented
        mro = getattr(C, '__mro__', None)
        if mro is None:  # Python 2 old-style class
        ...

C is a <type ‘unicode’> here. So we simply pass unicode string to logger and such error raised. Looks like this happened because of the following line in python2.7/logging/init.py:

if (args and len(args) == 1 and isinstance(args[0], collections.Mapping)

Could anybody help with this issue? What we are doing wrong? Thanks in advance.