text: # Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import inspect
  from collections.abc import Sequence
  
  
  class ComponentManager:
      """
      Implement a manager class to add the new component properly.
      The component can be added as either class or function type.
  
      Args:
          name (str): The name of component.
  
      Returns:
          A callable object of ComponentManager.
  
      Examples 1:
  
          from paddlex.paddleseg.cvlibs.manager import ComponentManager
  
          model_manager = ComponentManager()
  
          class AlexNet: ...
          class ResNet: ...
  
          model_manager.add_component(AlexNet)
          model_manager.add_component(ResNet)
  
          # Or pass a sequence alliteratively:
          model_manager.add_component([AlexNet, ResNet])
          print(model_manager.components_dict)
          # {'AlexNet': <class '__main__.AlexNet'>, 'ResNet': <class '__main__.ResNet'>}
  
      Examples 2:
  
          # Or an easier way, using it as a Python decorator, while just add it above the class declaration.
          from paddlex.paddleseg.cvlibs.manager import ComponentManager
  
          model_manager = ComponentManager()
  
          @model_manager.add_component
          class AlexNet: ...
  
          @model_manager.add_component
          class ResNet: ...
  
          print(model_manager.components_dict)
          # {'AlexNet': <class '__main__.AlexNet'>, 'ResNet': <class '__main__.ResNet'>}
      """
  
      def __init__(self, name=None):
          self._components_dict = dict()
          self._name = name
  
      def __len__(self):
          return len(self._components_dict)
  
      def __repr__(self):
          name_str = self._name if self._name else self.__class__.__name__
          return "{}:{}".format(name_str, list(self._components_dict.keys()))
  
      def __getitem__(self, item):
          if item not in self._components_dict.keys():
              raise KeyError("{} does not exist in availabel {}".format(
                  item, self))
          return self._components_dict[item]
  
      @property
      def components_dict(self):
          return self._components_dict
  
      @property
      def name(self):
          return self._name
  
      def _add_single_component(self, component):
          """
          Add a single component into the corresponding manager.
  
          Args:
              component (function|class): A new component.
  
          Raises:
              TypeError: When `component` is neither class nor function.
              KeyError: When `component` was added already.
          """
  
          # Currently only support class or function type
          if not (inspect.isclass(component) or inspect.isfunction(component)):
              raise TypeError(
                  "Expect class/function type, but received {}".format(
                      type(component)))
  
          # Obtain the internal name of the component
          component_name = component.__name__
  
          # Check whether the component was added already
          if component_name in self._components_dict.keys():
              raise KeyError("{} exists already!".format(component_name))
          else:
              # Take the internal name of the component as its key
              self._components_dict[component_name] = component
  
      def add_component(self, components):
          """
          Add component(s) into the corresponding manager.
  
          Args:
              components (function|class|list|tuple): Support four types of components.
  
          Returns:
              components (function|class|list|tuple): Same with input components.
          """
  
          # Check whether the type is a sequence
          if isinstance(components, Sequence):
              for component in components:
                  self._add_single_component(component)
          else:
              component = components
              self._add_single_component(component)
  
          return components
  
  
  MODELS = ComponentManager("models")
  BACKBONES = ComponentManager("backbones")
  DATASETS = ComponentManager("datasets")
  TRANSFORMS = ComponentManager("transforms")
  LOSSES = ComponentManager("losses")
  