flatten_json() missing 1 required positional argument: 'json'

[ghost]

I'm getting the error "flatten_json() missing 1 required positional argument: 'json'" when using it with one json argument like in the docs:

flatten_json(json)

Edit: It looks like the documentation should be updated, since now the code reads:

def flatten_json(
    form,
    json,
    parent_key='',
    separator='-',
    skip_unknown_keys=True
):