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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def DeregisterAttributeContainer(cls, attribute_container_class):
 """Deregisters an attribute container class. The attribute container classes are identified based on their lower case container type. Args: attribute_container_class (type):
 attribute container class. Raises: KeyError: if attribute container class is not set for the corresponding container type. """

    container_type = attribute_container_class.CONTAINER_TYPE.lower()
    if container_type not in cls._attribute_container_classes:
      raise KeyError(
          'Attribute container class not set for container type: '
          '{0:s}.'.format(attribute_container_class.CONTAINER_TYPE))

    del cls._attribute_container_classes[container_type]