code: def mean_length(infile, limit=None):
      '''Returns the mean length of the sequences in the input file. By default uses all sequences. To limit to the first N sequences, use limit=N'''
      total = 0
      count = 0
      seq_reader = sequences.file_reader(infile)
      for seq in seq_reader:
          total += len(seq)
          count += 1
          if limit is not None and count >= limit:
              break
  
      assert count > 0
      return total / counf mean_length(infile, limit=None):
      '''Returns the mean length of the sequences in the input file. By default uses all sequences. To limit to the first N sequences, use limit=N'''
      total = 0
      count = 0
      seq_reader = sequences.file_reader(infile)
      for seq in seq_reader:
          total += len(seq)
          count += 1
          if limit is not None and count >= limit:
              break
  
      assert count > 0
      return total / count
docs: Returns the mean length of the sequences in the input file. By default uses all sequences. To limit to the first N sequences, use limit=N