code: def increment(self, counter_name, delta):
      
      current_value = self.counters.get(counter_name, 0)
      new_value = current_value + delta
      self.counters[counter_name] = new_value
      return new_value
docs: Increment counter value.
  
      Args:
        counter_name: counter name as String.
        delta: increment delta as Integer.
  
      Returns:
        new counter value.