old_contents: import csv
  
  import mapdamage.seqtk as seqtk
  
  
  def write_base_comp(fasta, destination):
      """Calculates the total base composition across all sequences in 'fasta'
      and writes them to 'destination' as CSV.
      """
      bases = {"A": 0, "C": 0, "G": 0, "T": 0}
      for stats in seqtk.comp(str(fasta)):
          for key in bases:
              bases[key] += stats[key]
  
      # calculate the base frequencies
      ba_su = sum(bases.values())
      for key in bases:
          bases[key] = bases[key] / ba_su
  
      with open(destination, "wt", newline="") as handle:
          writer = csv.writer(handle)
  
          header = ["A", "C", "G", "T"]
          writer.writerow(header)
          writer.writerow(bases[key] for key in header)
  
  
  def read_base_comp(filename):
      """Read the base compition from a file created by write_base_comp
      """
      with open("names.csv", newline="") as csvfile:
          reader = csv.DictReader(csvfile)
          for row in reader:
              return row
  
      raise csv.Error("No rows found in %r" % (filename,))
  
new_contents: import csv
  
  import mapdamage.seqtk as seqtk
  
  
  def write_base_comp(fasta, destination):
      """Calculates the total base composition across all sequences in 'fasta'
      and writes them to 'destination' as CSV.
      """
      bases = {"A": 0, "C": 0, "G": 0, "T": 0}
      for stats in seqtk.comp(str(fasta)):
          for key in bases:
              bases[key] += stats[key]
  
      # calculate the base frequencies
      ba_su = sum(bases.values())
      for key in bases:
          bases[key] = bases[key] / ba_su
  
      with open(destination, "wt", newline="") as handle:
          writer = csv.writer(handle)
  
          header = ["A", "C", "G", "T"]
          writer.writerow(header)
          writer.writerow(bases[key] for key in header)
  
  
  def read_base_comp(filename):
      """Read the base compition from a file created by write_base_comp
      """
      with open(filename, newline="") as csvfile:
          reader = csv.DictReader(csvfile)
          for row in reader:
              return row
  
      raise csv.Error("No rows found in %r" % (filename,))
  
subject: fix use of wrong filename in read_base_comp