自定义树枝功能无法识别

I have a twig/timber function and the code doesn't shows any error but when I go to use function in my twig template there is an error saying '' is not a function.

This is what I have in my fucntions.php file in the twig template:

add_filter( 'timber/twig', function( \Twig_Environment $twig ) {
    $twig->addFunction( new Twig_Function( 'get_custom_meta', 'get_custom_meta' ) );

} );

function get_custom_meta($key,$id){
    if(empty($id)){
       return types_render_field($key,array("raw"=>"true","separator"=>";"));
    }else{
       return get_post_meta( $id, 'wpcf-'.$key, true );
    }
}

and this is how I'm calling the function in the template.

{{ function(get_custom_meta('facebook', event.post_id )) }}

This in in wordpress. Thanks

{{ get_custom_meta('facebook', event.post_id ) }}

I think you access functions like this rather than through function()

/**
 * My custom Twig functionality.
 *
 * @param Twig_Environment $twig
 * @return $twig
 */
add_filter( 'timber/twig', function( \Twig_Environment $twig ) {
    $twig->addFunction( new Twig_Function( 'edit_post_link', 'edit_post_link' ) );
} );

when you make a function available in Twig by using Timber\Twig_Function inside the timber/twig hook like this you use it like that

{# single.twig #}
<div class="admin-tools">
    {{ edit_post_link }}
</div>
{# Calls edit_post_link using default arguments #}

{# single-my-post-type.twig #}
<div class="admin-tools">
    {{ edit_post_link(null, '<span class="edit-my-post-type-link">') }}
</div>
{# Calls edit_post_link with all defaults, except for second argument #}

the function() is for wordpress functions

refer to: timber twig functions