code: def titleCounts(readsAlignments):
      
  
      titles = defaultdict(int)
      for readAlignments in readsAlignments:
          for alignment in readAlignments:
              titles[alignment.subjectTitle] += 1
      return titles
docs: Count the number of times each title in a readsAlignments instance is
      matched. This is useful for rapidly discovering what titles were matched
      and with what frequency.
  
      @param readsAlignments: A L{dark.alignments.ReadsAlignments} instance.
      @return: A C{dict} whose keys are titles and whose values are the integer
          counts of the number of reads that matched that title.