text: from abc import ABCMeta
  from abc import abstractmethod
  from six import add_metaclass
  
  from pacman.model.constraints.abstract_constraints.abstract_constraint \
      import AbstractConstraint
  
  
  @add_metaclass(ABCMeta)
  class AbstractKeyAllocatorConstraint(AbstractConstraint):
      """ A constraint on key allocation
      """
  
      def __init__(self, label):
          AbstractConstraint.__init__(self, label)
  
      def is_constraint(self):
          return True
  
      @abstractmethod
      def is_key_allocator_constraint(self):
          """ Determine if this is a key allocator constraint
          """
          pass
  