Checks if key is suitable for given request according to key type and request's user agent.

def is_suitable(self, request):
        """
        Checks if key is suitable for given request according to key type and request's user agent.
        """
        if self.key_type:
            validation = KEY_TYPE_VALIDATIONS.get( self.get_type() )
            return validation( request ) if validation else None
        return True