old_contents: class BaseExcelError(Exception):
  
      def __init__(self, message):
          super(BaseExcelError, self).__init__()
          self.message = message
  
  
  class ValidationError(BaseExcelError):
      pass
  
  
  class ColumnNotEqualError(BaseExcelError):
      pass
  
  
  class FieldNotExist(BaseExcelError):
      pass
  
new_contents: class BaseExcelError(Exception):
  
      def __init__(self, message):
          super(BaseExcelError, self).__init__()
          self.message = message
  
  
  class ValidationError(BaseExcelError):
      pass
  
  
  class ColumnNotEqualError(BaseExcelError):
      pass
  
  
  class FieldNotExist(BaseExcelError):
      pass
  
  
  class SerializerConfigError(BaseExcelError):
      pass
  
subject: Add error when serializer setup has error