Magento 2: Create multiselect product attribute

magento2_multiselect.php

<?php

['code' => 'code_of_the_attribute',
        'attribute_set' => '*',
        'label' => 'Concern',
        'attribute_group' => 'Extra Content',
        'type' => 'text',
        'input' => 'multiselect',
        'option' => ['values' => [
            'Option 1',
            'Option 2',
            'Option 3',
            ],
        ],
        'backend' => 'Magento\Eav\Model\Entity\Attribute\Backend\ArrayBackend',
        'unit' => '',
        'required' => false,
        'visible' => true,
        'visible_on_front' => false,
        'sort_order' => 2,
        'global' => \Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface::SCOPE_STORE,
        'searchable' => true,
        'filterable' => true,
        'used_for_promo_rule' => true,
        'comparable' => false,
        'wysiwyg_enabled' => false,
        'used_in_product_listing' => false,
        'used_for_sort_by' => false, ]