input: Write a python function to get the longest string from a list of strings.
  assert get_longest_string(["abc", "def", "ghij"]) == "ghij"
  assert get_longest_string(["hello", "world", "python"]) == "python"
  assert get_longest_string(["a", "ab", "abc", "abcd"]) == "abcd"
output: def get_longest_string(strings):
      if not strings:
          return ""
      return max(strings, key=len)