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 string with its cases swapped.
  assert convert_string_case("this Is A TeST")=="THIS iS a tEst"
  assert convert_string_case("Hello World")=="hELLO wORLD"
  assert convert_string_case("123 !@#")=="123 !@#"
  assert convert_string_case("")==""
  assert convert_string_case("a")=="A"
  assert convert_string_case("B")=="b"
output: def convert_string_case(s):
      return s.swapcase()