for-unpacking-the-dict-type-containers.py

headers = {
    'Accept': 'text/plain',
    'Content-Length': 348, 
    'Host': 'http://mingrammer.com' 
}  

def pre_process(**headers): 
    content_length = headers['Content-Length'] 
    print('content length: ', content_length) 
    
    host = headers['Host']
    if 'https' not in host: 
        raise ValueError('You must use SSL for http communication')  
        
pre_process(**headers)
# content length:  348
# Traceback (most recent call last):
#   File "<stdin>", line 1, in <module>
#   File "<stdin>", line 7, in pre_process
# ValueError: You must use SSL for http communication

This example is confusing and shows nothing about dict unpacking.
Shorter example like this is right usage of dict unpacking:

>>> def add(a=0, b=0):
...     return a + b
...
>>> d = {'a': 2, 'b': 3}
>>> add(**d)
5