old_contents: """ Tablib - DataFrame Support.
  """
  
  
  import sys
  
  
  if sys.version_info[0] > 2:
      from io import BytesIO
  else:
      from cStringIO import StringIO as BytesIO
  
  from pandas import DataFrame
  
  import tablib
  
  from tablib.compat import unicode
  
  title = 'df'
  extensions = ('df', )
  
  def detect(stream):
      """Returns True if given stream is a DataFrame."""
      try:
          DataFrame(stream)
          return True
      except ValueError:
          return False
  
  
  def export_set(dset, index=None):
      """Returns DataFrame representation of DataBook."""
      dataframe = DataFrame(dset.dict, columns=dset.headers)
      return dataframe
  
  
  def import_set(dset, in_stream):
      """Returns dataset from DataFrame."""
      dset.wipe()
      dset.dict = in_stream.to_dict(orient='records')
  
new_contents: """ Tablib - DataFrame Support.
  """
  
  
  import sys
  
  
  if sys.version_info[0] > 2:
      from io import BytesIO
  else:
      from cStringIO import StringIO as BytesIO
  
  try:
      from pandas import DataFrame
  except ImportError:
      DataFrame = None
  
  import tablib
  
  from tablib.compat import unicode
  
  title = 'df'
  extensions = ('df', )
  
  def detect(stream):
      """Returns True if given stream is a DataFrame."""
      if DataFrame is None:
          return False
      try:
          DataFrame(stream)
          return True
      except ValueError:
          return False
  
  
  def export_set(dset, index=None):
      """Returns DataFrame representation of DataBook."""
      if DataFrame is None:
          raise NotImplementedError(
              'DataFrame Format requires `pandas` to be installed.'
              ' Try `pip install tablib[pandas]`.')
      dataframe = DataFrame(dset.dict, columns=dset.headers)
      return dataframe
  
  
  def import_set(dset, in_stream):
      """Returns dataset from DataFrame."""
      dset.wipe()
      dset.dict = in_stream.to_dict(orient='records')
  
subject: Raise NotImplementedError if pandas is not installed