>>> def decorate(func):
...     print('decorating')
...     return func
>>> def add(a, b):
...     return a + b
>>> undecorated = add
>>> decorated = decorate(add)
decorating

#%%

>>> add
<function add at 0x106f04860>
>>> undecorated
<function add at 0x106f04860>
>>> decorated
<function add at 0x106f04860>

#%%

>>> add(1,2)
3
>>> undecorated(1,2)
3
>>> decorated(1,2)
3