# File rexml/parent.rb, line 129
    def insert_before( child1, child2 )
      if child1.kind_of? String
	child1 = XPath.first( self, child1 )
	child1.parent.insert_before child1, child2
      else
	ind = index(child1)
	@children[ind,0] = child2
	child2.parent = self
      end
      self
    end