docs: def update(self, id):
          """PUT /layertemplates/id: Update an existing item."""
          # url('LayerTemplates', id=ID)
          lt = meta.Session.query(LayerTemplate).get(id)
          # use following query for getting a layertemplate owned by current user
          #lt = self._get_lt_from_user_by_id(c.user, id)
          if lt is None:
              abort(404)
          content = request.environ['wsgi.input'].read(int(request.environ['CONTENT_LENGTH']))
          content = content.decode('utf8')
          content = simplejson.loads(content)        
          lt.name = content['name']
          lt.comment = content['comment']
          lt.json = content['json']
          meta.Session.commit()
          response.status = 201