cf.Field.extract

Field.extract(*args, **kwargs)

Return the instance if it matches the given conditions.

Equivalent to:

def extract(f, *args, **kwargs):
    if f.match(*args, **kwargs):
        return f
    raise ValueError``

Parameters :

*args, **kwargs :

As for the match method.

Returns :

out :

The variable as an object identity, if it matches the given conditions.

Raises :

ValueError :

If the variable does not match the conditions.