This takes a binary file for reading a pickle data stream.
The protocol version of the pickle is detected automatically, so no
protocol argument is needed. Bytes past the pickled object's
representation are ignored.
The argument *file* must have two methods, a read() method that takes
an integer argument, and a readline() method that requires no
arguments. Both methods should return bytes. Thus *file* can be a
binary file object opened for reading, an io.BytesIO object, or any
other custom object that meets this interface.
Optional keyword arguments are *fix_imports*, *encoding* and *errors*,
which are used to control compatibility support for pickle stream
generated by Python 2. If *fix_imports* is True, pickle will try to
map the old Python 2 names to the new names used in Python 3. The
*encoding* and *errors* tell pickle how to decode 8-bit string
instances pickled by Python 2; these default to 'ASCII' and 'strict',
respectively. The *encoding* can be 'bytes' to read these 8-bit
string instances as bytes objects.