input: Write a python function to find the string with the maximum length from a list of strings.
  assert max_length(['cat', 'primate', 'monkey']) == 'primate'
  assert max_length(['apple', 'banana', 'cherry']) == 'banana'
  assert max_length(['a', 'ab', 'abc', 'abcd']) == 'abcd'
output: def max_length(strings):
      return max(strings, key=len)