public function column_content( $column_name, $post_id ) {
		// Bail out.
		if ( empty( $this->columns )
			|| ! in_array( $column_name, array_keys( $this->columns ), true )
		) {
			return;
		}

		$column = $this->columns[ $column_name ];

		if ( 'thumbnail' === $column_name ) {
			$src = get_the_post_thumbnail_url( $post_id, 'thumbnail' );

			if ( empty( $src ) ) {
				return;
			}

			$styles = '';

			foreach ( [ 'width', 'height' ] as $attr ) {
				if ( isset( $column[ $attr ] ) ) {
					$styles .= $attr . ':' . $column[ $attr ] . 'px;';
				}
			}

			if ( ! empty( $styles ) ) {
				$styles = ' style="' . $styles . '"';
			}

			echo '<img src="' . esc_attr( $src ) . '"' . $styles . '>';

			return;
		}

		if ( 'acf' === $column['type'] ) {
			$value = get_field( $column_name, $post_id );
		} else {
			$value = get_post_meta( $post_id, $column_name, true );
		}

		if ( is_callable( $column['transform'] ) ) {
			$value = call_user_func( $column['transform'], $value, $post_id );
		}

		echo $value;
	}