input: Write a function to convert a given string to a different case using the swapcase() method. The function should take a string as input and return the new string with its case swapped.
  def convert_string_case(string):
      new_string = string.swapcase()
      return new_string
  
  assert convert_string_case("this Is A TeST")=="THIS iS a tEst"
  assert convert_string_case("HELLO world")=="hello WORLD"
  assert convert_string_case("")==""
  assert convert_string_case("12345")=="12345"
  assert convert_string_case("Python Code")=="pYTHON cODE"
output: def convert_string_case(string):
      new_string = string.swapcase()
      return new_string