Don't use __code__ to detect Python callable object

[buckle2000]

Expected Behavior

dlib.find_max_global (Python) should work on every callable object.

Current Behavior

It only works on objects with attribute __code__.

Steps to Reproduce

import dlib
from functools import partial
def f(arg0):
    return 0
dlib.find_max_global(partial(f, 2), [0.], [1.], 100)

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-112-da98f75572a0> in <module>
----> 1 dlib.find_max_global(partial(f, 2), [0.], [1.], 100)

AttributeError: 'functools.partial' object has no attribute '__code__'

• Version: dlib==19.19.0 (Python package)
• Where did you get dlib: pip/pypi
• Platform: Linux 5.0.0-38-generic #41-Ubuntu
• Compiler: gcc version 8.3.0 (Ubuntu 8.3.0-6ubuntu1)

[buckle2000]

Suggestion: https://docs.python.org/3/library/functions.html#callable

[davisking]

That would be cool. You should submit a PR :)

[buckle2000]

But I don't know C++ :face_with_head_bandage: