public function getAttributes($book): array
    {
        return [
            "title" => function (array $book) {
                return $book["title"];
            },
            "isbn13" => function (array $book) {
                return $book["isbn13"];
            },
            "releaseDate" => function (array $book) {
                return $book["release_date"];
            },
            "hardCover" => function (array $book) {
                return $book["hard_cover"];
            },
            "pages" => function (array $book) {
                return (int) $book["pages"];
            },
        ];
    }
public function getAttributes($book): array
    {
        return [
            "title" => function (array $book) {
                return $book["title"];
            },
            "isbn13" => function (array $book) {
                return $book["isbn13"];
            },
            "releaseDate" => function (array $book) {
                return $book["release_date"];
            },
            "hardCover" => function (array $book) {
                return $book["hard_cover"];
            },
            "pages" => function (array $book) {
                return (int) $book["pages"];
            },
        ];
    }
public function getAttributes ( $ book ) : array { return [ "title" => function ( array $ book ) { return $ book [ "title" ] ; } , "isbn13" => function ( array $ book ) { return $ book [ "isbn13" ] ; } , "releaseDate" => function ( array $ book ) { return $ book [ "release_date" ] ; } , "hardCover" => function ( array $ book ) { return $ book [ "hard_cover" ] ; } , "pages" => function ( array $ book ) { return ( int ) $ book [ "pages" ] ; } , ] ; }
Provides information about the "attributes" member of the current resource.

The method returns an array of attributes if you want the section to
appear in the response or null if it should be omitted. In the returned array,
the keys signify the attribute names, while the values are callables receiving the
domain object as an argument, and they should return the value of the corresponding
attribute.

@param array $book
@return callable[]
Provides information about the attributes member of the current resource .