text: from __future__ import annotations
  from typing import TYPE_CHECKING
  import typing
  if TYPE_CHECKING:
      from . import Container
  
  class Layer:
  
      def __init__(self):
          self.contains_types:typing.Dict[str, Container] = dict()
  
      def attach(self, container: Container):
          if not container.of_type in self.contains_types:
              self.contains_types[container.of_type] = container
          else:
              print("Container of Type: {} already exists".format(container.of_type))
  
      def __getitem__(self, item) -> Container:
          return self.contains_types[item]
  
      def update(self):
          for item in self.contains_types.items():
              item[1].update()