WordPress doesn't include css

I want load a custom css in the index.php file, this is my code in function.php

if(! function_exists('basictheme_styles_scripts')) {
    function basictheme_styles_scripts() {
        wp_enqueue_script('jquery');
        wp_enqueue_style('basictheme-opensans', '//fonts.googleapis.com/css?family=Open+Sans');
        wp_enqueue_style( 'basictheme', get_template_directory_uri().'/style.css');

    }
}
add_action('wp_enqueue_scripts','basictheme_styles_scripts');

but perhaps something is wrong, beacause my index doesn’t load it

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