python: simplify code

Author: yoff

python/ql/src/experimental/Security/CWE-022bis/TarSlipImprov.ql

@@ -100,22 +100,15 @@ class Configuration extends TaintTracking::Configuration {
   }
 
   override predicate isAdditionalTaintStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
-    exists(AttrRead attr, MethodCallNode call |
-      attr.accesses(nodeFrom, "getmembers") and
-      nodeFrom = call.getObject() and
-      nodeFrom instanceof AllTarfileOpens and
-      nodeTo = call
-    )
+    nodeTo.(MethodCallNode).calls(nodeFrom, "getmembers") and
+    nodeFrom instanceof AllTarfileOpens
     or
     // To handle the case of `with closing(tarfile.open()) as file:`
     // we add a step from the first argument of `closing` to the call to `closing`,
     // whenever that first argument is a return of `tarfile.open()`.
-    exists(API::CallNode closing |
-      closing = API::moduleImport("contextlib").getMember("closing").getACall() and
-      nodeFrom = closing.getArg(0) and
-      nodeFrom = tarfileOpen().getReturn().getAValueReachableFromSource() and
-      nodeTo = closing
-    )
+    nodeTo = API::moduleImport("contextlib").getMember("closing").getACall() and
+    nodeFrom = nodeTo.(API::CallNode).getArg(0) and
+    nodeFrom = tarfileOpen().getReturn().getAValueReachableFromSource()
   }
 }