* Fixes a corner case bug when a wrapper object of a
  composed function is composed. In those situations:
  * `isinstance(function, composed)` could be true;
  * `function` is the wrapper instead of being the
    composed function instance;
  * `function.__wrapped__` is the composed function
    instance instead of being the innermost function.
* Performance-wise, this fix performs better on well
  optimizing Python implementations (PyPy, Cython)
  than alternatives which peform negligibly better on
  barely-optimizing Python implementations (CPython),
  and is at worst negligibly worse than the pre-fix
  version.

This reverts commit a10c194e8b73d9451808a08d366e5c3e1c2c4d35.