docs: def filter_data(df, filter_name, verbose=False):
      "Filter certain entries with given name."
  
      # pick only entries ending with 'Berlin' in column stop_name, incl. '(Berlin)' 
      # df = df[df.stop_name.apply(lambda cell: 'Berlin' in cell)]
      df = df[df.stop_name.apply(
          lambda cell: filter_name.encode('utf-8') in cell)]
  
      # remove ' (Berlin)' in column stop_name
      # df.stop_name = df.stop_name.apply(lambda cell: re.sub(' \(Berlin\)', '', cell))
  
      # remove initial 'S' and 'U' and 'S+U' in column stop_name
      # this creates a warning!
      # df.stop_name = df.stop_name.apply(lambda cell: re.sub('^([S\+U]+) +(.*)', lambda m: m.groups()[1], cell))
  
      if verbose:
          msg = '- Filtered down to %d entries containing "%s".'
          print(msg % (len(df), filter_name))
  
      return df