<?php
/**
 * Provides a 'SLS Block' Block
 *
 * @Block(
 *   id = "SLS-Subheader",
 *   admin_label = @Translation("SLS Subheader"),
 * )
 */

namespace DrupalsubheaderPluginBlock;

use DrupalCoreBlockBlockBase;

class SubheaderBlock extends BlockBase {
  /**
   * {@inheritdoc}
   */
  public function build() {


    return array(
      '#title' => "test",
    );
  }
}
?>

<?php
/**
 * Implements hook_theme().
*/

function subheader_theme() {
  return array(
    'slssubheader' => array(
      'variables' => array('pierre' => NULL),
      'template' => 'specifictemplate',
    ),
  );
}