text: from codewars.kyu4.twice_linear import dbl_linear
  
  
  class TestTwiceLinear():
      
      def test_twice_linear(self):  
          assert dbl_linear(10) == 22
          assert dbl_linear(20) == 57
          assert dbl_linear(30) == 91
          assert dbl_linear(50) == 175
  