code: def exists_evaluator(self, index):
      
      attr_name = self.condition_data[index][0]
      return self.attributes.get(attr_name) is not None
docs: Evaluate the given exists match condition for the user attributes.
  
        Args:
          index: Index of the condition to be evaluated.
  
        Returns:
          Boolean: True if the user attributes have a non-null value for the given condition,
                   otherwise False.