input: from typing import List
  
  def sort_by_length(strings: List[str]) -> List[str]:
      """ Sorts a list of strings based on their length.
      >>> sort_by_length(["Hello","World!","Good","Morning"])
      ["Good", "Hello", "World!", "Morning"]
      """
      strings.sort(key=len)
      return strings
output:     strings.sort(key=len)
      return strings