input: Write a function to concatenate two strings "Hello" and "World" and print them in the same line. The function should return the concatenated string.
  
  def print_strings():
      string1 = "Hello"
      string2 = "World"
      result = string1 + " " + string2
      print(result)
      return result
  
  assert print_strings()=="Hello World"
output: def print_strings():
      string1 = "Hello"
      string2 = "World"
      result = string1 + " " + string2
      print(result)
      return result