def index element
      rv = 0
      found = @element.find do |child|
        child.kind_of? Element and
        (rv += 1) and
        child == element
      end
      return rv if found == element
      return -1
    end
def index element
      rv = 0
      found = @element.find do |child|
        child.kind_of? Element and
        (rv += 1) and
        child == element
      end
      return rv if found == element
      return -1
    end
Returns the index of the supplied child (starting at 1), or -1 if
 the element is not a child
 element:: an +Element+ child