human
I wrote the below code

    if (mode != 'r'):
        raise ValueError(('bad    mode    %r' % mode))
    exclusive_fp = False
    filename = ''
    if isPath(fp):
        filename = fp
    else:
        try:
            from pathlib import Path
            if isinstance(fp, Path):
                filename = str(fp.resolve())
        except ImportError:
            pass
    if filename:
        fp = builtins.open(filename, 'rb')
        exclusive_fp = True
    try:
        fp.seek(0)
    except (AttributeError, io.UnsupportedOperation):
        fp = io.BytesIO(fp.read())
        exclusive_fp = True
    prefix = fp.read(16)
    preinit()
    def _open_core(fp, filename, prefix):
        for i in ID:
            try:
                (factory, accept) = OPEN[i]
                if ((not accept) or accept(prefix)):
                    fp.seek(0)
                    im = factory(fp, filename)
                    _decompression_bomb_check(im.size)
                    return im
            except (SyntaxError, IndexError, TypeError, struct.error):
                continue
        return None
    im = _open_core(fp, filename, prefix)
    if (im is None):
        if init():
            im = _open_core(fp, filename, prefix)
    if im:
        im._exclusive_fp = exclusive_fp
        return im
    if exclusive_fp:
        fp.close()
    raise IOError(('cannot    identify    image    file    %r' % (filename if filename else fp)))

What's a good function header?
 ... What is a Python code to fix = fp?
assistant
#Here is Python code to fix = fp.

def open(fp, mode='r'):