I’m going to assume by your example that you already have the response converted to Python datatypes (responses returned by requests have a .json() method to try if not).
Python dictionaries have a .items() method that returns an iterator of key-value pairs in a dictionary that works well for purposes such as this.
new_dictionary = {}
for key, value in old_dictionary.items():
new_key = camel_to_snake(key)
new_dictionary[new_key] = value
Or, more concisely using comprehensions
new_dictionary = {camel_to_snake(key): value for key, value in old_dictionary.items()}