def find(self, _id, instance = None):
        """ Find
        
        Args:
            _id (str): instance id or binding Id
            
        Keyword Arguments:
            instance (AtlasServiceInstance.Instance): Existing instance
            
        Returns:
            AtlasServiceInstance.Instance or AtlasServiceBinding.Binding: An instance or binding. 
        """
        
        if instance is None:
            # We are looking for an instance
            return self.service_instance.find(_id)
        else:
            # We are looking for a binding
            return self.service_binding.find(_id, instance)