code: def filter(func, data):
      
  
      out = []
      for r in data:
          if func(r):
              out.append(r)
      return out
docs: Parameter <func> must be a single-argument
      function that takes a sequence (i.e.,
  a sample point) and returns a boolean. This procedure calls <func> on
  each element in <data> and returns a list comprising elements for
  which <func> returns True.
  
  >>> data = [[1,5], [2,10], [3,13], [4,16]]
  ... chart_data.filter(lambda x: x[1] % 2 == 0, data)
  [[2,10], [4,16]].