code: def update_dict_sum(input_dict,key,increment=None,initial_value=None):
      '''update_dict sum will increment a dictionary key 
      by an increment, and add a value of 0 if it doesn't exist
      :param input_dict: the dict to update
      :param increment: the value to increment by. Default is 1
      :param initial_value: value to start with. Default is 0
      '''
      if increment == None:
          increment = 1
  
      if initial_value == None:
          initial_value = 0
  
      if key in input_dict:
          input_dict[key] += increment
      else:
          input_dict[key] = initial_value + increment
      return input_dicf update_dict_sum(input_dict,key,increment=None,initial_value=None):
      '''update_dict sum will increment a dictionary key 
      by an increment, and add a value of 0 if it doesn't exist
      :param input_dict: the dict to update
      :param increment: the value to increment by. Default is 1
      :param initial_value: value to start with. Default is 0
      '''
      if increment == None:
          increment = 1
  
      if initial_value == None:
          initial_value = 0
  
      if key in input_dict:
          input_dict[key] += increment
      else:
          input_dict[key] = initial_value + increment
      return input_dict
docs: update_dict sum will increment a dictionary key 
      by an increment, and add a value of 0 if it doesn't exist
      :param input_dict: the dict to update
      :param increment: the value to increment by. Default is 1
      :param initial_value: value to start with. Default is 0