current_user_can( ‘edit_post’, $post_id ) does not work for contributer but for administrator

using map_meta_cap I added edit_post per post cap to user

function my_map_meta_cap( $caps, $cap, $user_id, $args ){
    if ( 'edit_post' == $cap ) {
        $post = get_post( $args[0] );
        $post_type = get_post_type_object( $post->post_type );
        $caps = array();
        if ( $user_id == $post->post_author )
            $caps[] = $post_type->cap->edit_posts;
        else
            $caps[] = $post_type->cap->edit_others_posts;
    }
    return $caps;
}
add_filter( 'map_meta_cap', 'my_map_meta_cap', 10, 4 );