code: def find_common_root(elements):
      
      if not elements:
          raise UserWarning("Can't find common root - no elements suplied.")
  
      root_path = el_to_path_vector(elements.pop())
  
      for el in elements:
          el_path = el_to_path_vector(el)
  
          root_path = common_vector_root(root_path, el_path)
  
          if not root_path:
              raise UserWarning(
                  "Vectors without common root:\n%s" % str(el_path)
              )
  
      return root_path
docs: Find root which is common for all `elements`.
  
      Args:
          elements (list): List of double-linked HTMLElement objects.
  
      Returns:
          list: Vector of HTMLElement containing path to common root.