code: def _operator_count(self, individual):
          
          operator_count = 0
          for i in range(len(individual)):
              node = individual[i]
              if type(node) is deap.gp.Primitive and node.name != 'CombineDFs':
                  operator_count += 1
          return operator_count
docs: Count the number of pipeline operators as a measure of pipeline complexity.
  
          Parameters
          ----------
          individual: list
              A grown tree with leaves at possibly different depths
              dependending on the condition function.
  
          Returns
          -------
          operator_count: int
              How many operators in a pipeline