code: def update_subtotals(self, current, sub_key):
          
  
          if not self.sub_counts.get(sub_key):
              self.sub_counts[sub_key] = {}
          for item in current:
              try:
                  self.sub_counts[sub_key][item] += 1
              except KeyError:
                  self.sub_counts[sub_key][item] = 1
docs: updates sub_total counts for the class instance based on the
              current dictionary counts
  
          args:
          -----
              current: current dictionary counts
              sub_key: the key/value to use for the subtotals