the
        given protocol; supported protocols are 0, 1, 2, 3, 4 and 5.
        The default protocol is 4. It was introduced in Python 3.4, and
        is incompatible with previous versions.

        Specifying a negative protocol version selects the highest
        protocol version supported.  The higher the protocol used, the
        more recent the version of Python needed to read the pickle
        produced.

        The *file* argument must have a write() method that accepts a
        single bytes argument. It can thus be a file object opened for
        binary writing, an io.BytesIO instance, or any other custom
        object that meets this interface.

        If *fix_imports* is True and *protocol* is less than 3, pickle
        will try to map the new Python 3 names to the old module names
        used in Python 2, so that the pickle data stream is readable
        with Python 2.

        If *buffer_callback* is None (the default), buffer views are
        serialized into *file* as part of the pickle stream.

        If *buffer_callback* is not None, then it can be called any number
        of times with a buffer view.  If the callback returns a false value
        (such as None), the given buffer is out-of-band; otherwise the
        buffer is serialized in-band, i.e. inside the pickle stream.

        It is an error if *buffer_callback* is not None and *protocol*
        is None or smaller than 5.
        Nr