code: def test_vars(self):
      vars = {"x": "X", "y": "YYY"}
      self.assertEqual("XYYY", ninja_syntax.expand("$x$y", vars))
  
imports: import unittest
  import ninja_syntax
label_desc: Use image node_id 3 for calling the TestExpand obj's underlying member method code with example usage: obj.test_vars() without return types