docs: def transform(func, data):
      """Apply <func> on each element in <data> and return the list
  consisting of the return values from <func>.
  
  >>> data = [[10,20], [30,40], [50,60]]
  ... chart_data.transform(lambda x: [x[0], x[1]+1], data)
  [[10, 21], [30, 41], [50, 61]]
  
  """
      out = []
      for r in data:
          out.append(func(r))
      return out