getRemovedPostUpdates example

$regexp = '/^(?<extension>.+)_' . $this->updateType . '_(?<name>.+)$/';
    $functions = get_defined_functions();

    $updates = [];
    foreach (preg_grep('/_' . $this->updateType . '_/', $functions['user']) as $function) {
      // If this function is an extension update function, add it to the list of       // extension updates.       if (preg_match($regexp, $function, $matches)) {
        if (in_array($matches['extension'], $this->enabledExtensions)) {
          $function_name = $matches['extension'] . '_' . $this->updateType . '_' . $matches['name'];
          if ($this->updateType === 'post_update') {
            $removed = array_keys($this->getRemovedPostUpdates($matches['extension']));
            if (array_search($function_name, $removed) !== FALSE) {
              throw new RemovedPostUpdateNameException(sprintf('The following update is specified as removed in hook_removed_post_updates() but still exists in the code base: %s', $function_name));
            }
          }
          $updates[] = $function_name;
        }
      }
    }
    // Ensure that the update order is deterministic.     sort($updates);
    return $updates;
  }