Filter Widget Post query

/**
 *
 * Filter Widget Post query
 *
 * @param array $query_args
 * @param array $instance
 *
 */
add_filter( 'streamtube/core/widget/posts/query_args', function(  $query_args, $instance ){

    /**
     *
     * Holds the custom taxonomy slug(s), for instance: custom-taxonomy-slug or array( 'custom-taxonomy-slug' )
     *
     * @var string|array
     */
    $taxonomy = 'custom-taxonomy-slug';

    // Holds the widget ID
    $widget_id = 'posts-widget-9';

    // Holds relation
    $relation = 'AND'; // or OR

    if( array_key_exists( 'id', $instance ) && $instance['id'] == $widget_id ){

        if( $query_args['tax_query'] ){

            unset( $query_args['tax_query']['relation'] );

            if( is_string( $taxonomy ) ){
                $taxonomy = array( $taxonomy );
            }

            $tax_query = compact( 'relation' );

            for ( $i=0; $i < count( $query_args['tax_query'] ); $i++) {
                if( is_array( $query_args['tax_query'][$i] ) ){
                    if( in_array( $query_args['tax_query'][$i]['taxonomy'], $taxonomy ) ){
                        $tax_query[] = $query_args['tax_query'][$i];
                    }
                }
            }
        }

        if( $tax_query ){
            $query_args = array_merge( $query_args, compact( 'tax_query' ) );
        }
    }

    return $query_args;

}, 10, 2 );