def render(id, template_path, input):
    """Render a template.

        id - the id for the collection
        template_path - the relative path (or filename) of the template
                        itself, under the path of the collection
        input - input data for the template

        If the template raises a CompileError or RenderError, the
        system will automatically fall back on the original
        non-customized template.
        """
