code: def findFileRtiIndex(self, childIndex):
          
          parentIndex = childIndex.parent()
          if not parentIndex.isValid():
              return childIndex
          else:
              parentItem = self.getItem(parentIndex)
              childItem = self.getItem(childIndex)
              if parentItem.fileName == childItem.fileName:
                  return self.findFileRtiIndex(parentIndex)
              else:
                  return childIndex
docs: Traverses the tree upwards from the item at childIndex until the tree
              item is found that represents the file the item at childIndex