Finds the nearest enclosing function-definition node for the given id by walking up the AST parent chain.
Used by includeCallees to detect the function-definition boundary a node sits inside, as backward slicing
does not otherwise visit the function-definition vertex itself (nothing within the body links to it).
Finds the nearest enclosing function-definition node for the given id by walking up the AST parent chain. Used by
includeCalleesto detect the function-definition boundary a node sits inside, as backward slicing does not otherwise visit the function-definition vertex itself (nothing within the body links to it).