code: def count_terms(geneset, assoc, obo_dag):
      
      term_cnt = Counter()
      for gene in (g for g in geneset if g in assoc):
          for goid in assoc[gene]:
              if goid in obo_dag:
                  term_cnt[obo_dag[goid].id] += 1
  
      return term_cnt
docs: count the number of terms in the study group