'Ensure client_id belong to a valid and active client.
Note, while not strictly necessary it can often be very convenient
to set request.client to the client object associated with the
given client_id.
:param request: oauthlib.common.Request
:rtype: True or False
Method is used by:
- Authorization Code Grant
- Implicit Grant'

def validate_client_id(self, client_id, request, *args, **kwargs):

    raise NotImplementedError(u'Subclasses    must    implement    this    method.')
