/**
 * Implements hook_block_view_alter().
 */
function {{ machine_name }}_block_view_alter(&$data, $block) {
  // Remove the contextual links on all blocks that provide them.
  if (is_array($data['content']) && isset($data['content']['#contextual_links'])) {
    unset($data['content']['#contextual_links']);
  }
  // Add a theme wrapper function defined by the current module to all blocks
  // provided by the "somemodule" module.
  if (is_array($data['content']) && $block->module == 'somemodule') {
    $data['content']['#theme_wrappers'][] = 'mymodule_special_block';
  }
}