Refactor preview result structure and update tests to validate preview field with nested latex and sympy fields.

Author: m-messer

evaluation_function/preview.py

@@ -22,4 +22,4 @@ def preview_function(response: Any, params: Params) -> Result:
     split into many) is entirely up to you.
     """
 
-    return Result(Preview(latex = response, sympy = response))
+    return Result(preview=Preview(latex=response,sympy=response))

evaluation_function/preview_test.py

@@ -25,7 +25,9 @@ def test_preview(self):
         response, params = "A", Params()
         result = preview_function(response, params)
 
-        self.assertIn("latex", result)
-        self.assertIn('sympy', result)
-        self.assertIsNotNone(result["latex"])
-        self.assertIsNotNone(result["sympy"])
+        self.assertIn('preview', result)
+        self.assertIsNotNone(result['preview'])
+        self.assertIn("latex", result['preview'])
+        self.assertIn('sympy', result['preview'])
+        self.assertIsNotNone(result["preview"]['latex'])
+        self.assertIsNotNone(result["preview"]['sympy'])