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Update `RegexExecution` docs and use `flowsTo()` instead of `getALocalSource()`.

Co-authored-by: yoff <lerchedahl@gmail.com>

python/ql/src/experimental/semmle/python/Concepts.qll

@@ -17,7 +17,7 @@ private import experimental.semmle.python.Frameworks
 /** Provides classes for modeling Regular Expression-related APIs. */
 module RegexExecution {
   /**
-   * A data-flow node that collects methods immediately executing an expression.
+   * A data-flow node that executes a regular expression.
    *
    * Extend this class to model new APIs. If you want to refine existing API models,
    * extend `RegexExecution` instead.

python/ql/src/experimental/semmle/python/frameworks/Stdlib.qll

@@ -60,7 +60,7 @@ private module Re {
       exists(DataFlow::CallCfgNode patternCall, DataFlow::AttrRead reMethod |
         this.getFunction() = reMethod and
         patternCall = API::moduleImport("re").getMember("compile").getACall() and
-        patternCall = reMethod.getObject().getALocalSource() and
+        patternCall.flowsTo(reMethod.getObject()) and
         reMethod.getAttributeName() instanceof RegexExecutionMethods and
         regexNode = patternCall.getArg(0)
       )