code2.py

def groupBy(func):
  def inner(data):
    assert isinstance(data,list) 
    temp_dict={}
    for value in data:
      if func(value) not in temp_dict:
          temp_dict[func(value)]=[value]
      else:
          temp_dict[func(value)].append(value)
    return temp_dict
  return inner

def test_group_by():
  data=groupBy(lambda x: x%2)([1,2,3])
  assert data == {1:[1,3], 0:[2]}
  data=groupBy(lambda x: x%2)([])
  assert data == {}
  data=groupBy(lambda x: x%2)(None)
  # raise assert error