input: Write a python function to normalize a list of strings by converting each to lowercase and stripping any leading or trailing whitespaces.
  assert normalize(["  Hello", "WORLD  ", "  PyTHon "]) == ["hello", "world", "python"]
  assert normalize(["TESTING", "  is", "fun  "]) == ["testing", "is", "fun"]
  assert normalize([" Normalize", "  THIs  ", " LiSt  "]) == ["normalize", "this", "list"]
output: def normalize(strings):
      return [s.strip().lower() for s in strings]