old_contents: #!/usr/bin/env python2
  
  from __future__ import division
  
  def reverse(seq):
      """Return the reverse of the given sequence (i.e. 3' to 
      5')."""
      return seq[::-1]
  
  def complement(seq):
      """Return the complement of the given sequence (i.e. G=>C, 
      A=>T, etc.)"""
      from string import maketrans
      complements = maketrans('ACTGactg', 'TGACtgac')
      return seq.translate(complements)
  
  def reverse_complement(seq):
      """Return the reverse complement of the given sequence 
      (e.g.  the opposite strand)."""
      return reverse(complement(seq))
  
  # This function contains a bug.  Do you see it?
  def gc_content(seq):
      """Return the GC content of the given sequence (e.g. the 
      fraction of nucleotides that are either G or C)."""
      return sum(x in 'GC' for x in seq) / len(seq)
  
  
new_contents: #!/usr/bin/env python2
  
  def reverse(seq):
      """Return the reverse of the given sequence (i.e. 3' to 
      5')."""
      return seq[::-1]
  
  def complement(seq):
      """Return the complement of the given sequence (i.e. G=>C, 
      A=>T, etc.)"""
      from string import maketrans
      complements = maketrans('ACTGactg', 'TGACtgac')
      return seq.translate(complements)
  
  def reverse_complement(seq):
      """Return the reverse complement of the given sequence 
      (e.g.  the opposite strand)."""
      return reverse(complement(seq))
  
  # This function contains a bug.  Do you see it?
  def gc_content(seq):
      """Return the GC content of the given sequence (e.g. the 
      fraction of nucleotides that are either G or C)."""
      return sum(x in 'GC' for x in seq) / len(seq)
  
  
subject: Put the gc_content bug back.