old_contents: # coding: utf8
  
  from core.ParsingEntities import Entity
  
  
  class ModificationEntity(Entity):
      def __add__(self, other):
          if isinstance(self, ModificationEntity) and isinstance(other, ModificationEntity):
              modification_operator = ModificationOperator()
              return modification_operator
          else:
              raise TypeError("Operands have to be ModificationEntity's subclasses")
  
  
  class ModificationCondition(ModificationEntity):
      pass
  
  
  class ModificationOperator(ModificationEntity):
      pass
new_contents: # coding: utf8
  
  from core.ParsingEntities import Entity
  
  
  class ModificationEntity(Entity):
      def __add__(self, other):
          if isinstance(self, ModificationEntity) and isinstance(other, ModificationEntity):
              modification_operator = ModificationOperator()
              return modification_operator
          else:
              raise TypeError("Operands have to be ModificationEntity's subclasses")
  
  
  class ModificationOperator(ModificationEntity):
      def __init__(self, operand_a, operand_b):
          self.operandA = operand_a
          self.operandB = operand_b
  
      def check(self, element, ref_position):
          pass
  
  
  class ModificationCondition(ModificationEntity):
      def __init__(self, character, operation_type, rel_position=0):
          self.rel_position = rel_position
          self.operationType = operation_type
          self.character = character
  
      def check(self, element, ref_position=0):
          pass
  
subject: Implement ModificationOperator and ModificationCondition classes