def diff(list1, list2):
  """
  Returns the list of entries that are present in list1 but not
  in list2.

  Args:
    list1 A list of elements
    list2 Another list of elements

  Returns:
    A list of elements unique to list1
  """
  diffed_list = []
  for item in list1:
    if item not in list2:
      diffed_list.append(item)
  return diffed_list