old_contents: import os
  import yaml
  from .cassette import Cassette
  
  
  def load_cassette(cassette_path):
      try:
          pc = yaml.load(open(cassette_path))
          cassette = Cassette(pc)
          return cassette
      except IOError:
          return None
  
  
  def save_cassette(cassette_path, cassette):
      dirname, filename = os.path.split(cassette_path)
      if not os.path.exists(dirname):
          os.makedirs(dirname)
      with open(cassette_path, 'a') as cassette_file:
          cassette_file.write(yaml.dump(cassette.serialize()))
  
new_contents: import os
  import yaml
  from .cassette import Cassette
  
  # Use the libYAML versions if possible
  try:
      from yaml import CLoader as Loader, CDumper as Dumper
  except ImportError:
      from yaml import Loader, Dumper
  
  
  def load_cassette(cassette_path):
      try:
          pc = yaml.load(open(cassette_path), Loader=Loader)
          cassette = Cassette(pc)
          return cassette
      except IOError:
          return None
  
  
  def save_cassette(cassette_path, cassette):
      dirname, filename = os.path.split(cassette_path)
      if not os.path.exists(dirname):
          os.makedirs(dirname)
      with open(cassette_path, 'a') as cassette_file:
          cassette_file.write(yaml.dump(cassette.serialize(), Dumper=Dumper))
  
subject: Use the libYAML version of yaml if it's available