reverted back to normal preview function

Author: ashwin6-dev

evaluation_function/preview.py

@@ -26,4 +26,16 @@ def preview_function(response: Any, params: Params) -> Result:
     split into many) is entirely up to you.
     """
 
-    return Result(preview=Preview(latex=r"p \land q", sympy="And(p, q)"))
+    feedback   = None
+    is_correct = False
+
+    # parse response into Formula
+    try:
+        formula = formula_parser(response)
+    
+    except BuildError as e:
+        return Result(preview=Preview(feedback = str(e)))
+    except ValueError as e:
+        return Result(preview=Preview(feedback = str(e)))
+
+    return Result(preview=Preview(latex=response, sympy=response))