Update expressions.py

Author: UV

pandas/core/computation/expressions.py

@@ -257,7 +257,7 @@ def where(cond, left_op, right_op, use_numexpr: bool = True):
         Whether to try to use numexpr.
     """
     assert _where is not None
-        string
+    
     return (
         _where(cond, left_op, right_op)
         if use_numexpr
@@ -267,7 +267,6 @@ def where(cond, left_op, right_op, use_numexpr: bool = True):
         return _where(cond, left_op, right_op)
     else:
         return _where_standard(cond, left_op, right_op)
-        main
 
 
 def set_test_mode(v: bool = True) -> None: