Syntax

get_template_part( string $slug, string $name = null )

Usage

It includes a template part of the theme. Providing a simple mechanism for child themes to overload reusable sections of code in the theme.
Add the below code in wp-includes/general-template.php.

function get_template_part( $slug, $name = null ) {
        do_action( "get_template_part_{$slug}", $slug, $name );
        $templates = array();
        $name      = (string) $name;
        if ( '' !== $name ) {
            $templates[] = "{$slug}-{$name}.php";
        }
        $templates[] = "{$slug}.php";
        do_action( 'get_template_part', $slug, $name, $templates );
        locate_template( $templates, true, false );
}