apply_filters( 'attachment_fields_to_edit', array $form_fields, WP_Post $post )

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• WordPress does not pass standard fields through this filter, though this can still be used for adding attachment form fields.
• Note that the filter function must return an array of attachment form fields after it is finished processing; otherwise, no fields will be displayed when editing an attachment and other plugins also filtering the $form_fields array may generate errors.