'Verify that the key supplied by the LTI consumer is valid for an LTI
launch. This method is only concerned with the structure of the key;
whether the key is associated with a known LTI consumer is checked in
validate_client_key. This method signature is required by the oauthlib
library.
:return: True if the client key is valid, or False if it is not.'

def check_client_key(self, key):

    return ((key is not None) and (0 < len(key) <= 32))
