'Render a parent block.'

def super(self, name, current):

    try:
        blocks = self.blocks[name]
        index = (blocks.index(current) + 1)
        blocks[index]
    except LookupError:
        return self.environment.undefined(('there    is    no    parent    block    called    %r.' % name), name='super')
    return BlockReference(name, self, blocks, index)
