docs: def remove_instance(self, instance):
          """ Remove an instance
          
          Remove an object from the MongoDB storage for caching
          
          Args:
              instance (AtlasServiceInstance.Instance): instance
          
          Raises:
              ErrStorageMongoConnection: Error during MongoDB communication.
              ErrStorageRemoveInstance: Failed to remove the instance.
          """
          
          # query
          query = { "instance_id" : instance.instance_id, "binding_id" : { "$exists" : False } }
          
          # delete the instance
          try:
              result = self.broker.delete_one(query)
          except:
              raise ErrStorageMongoConnection("Remove Instance")
          
          # return the result
          if result is not None and result.deleted_count == 1:
              instance.provisioned = False
          else:
              raise ErrStorageRemoveInstance(instance.instance_id)