'Validates a verification code.
OAuth providers issue a verification code to clients after the
resource owner authorizes access. This code is used by the client to
obtain token credentials and the provider must verify that the
verifier is valid and associated with the client as well as the
resource owner.'

def validate_verifier(self, client_key, request_token, verifier):

    raise NotImplementedError('Subclasses    must    implement    this    function.')
