Overrides ArrayElement::parse()
Overrides ArrayElement::parse
protected function parse() {
  $elements = array();
  foreach ($this->definition['mapping'] as $key => $definition) {
    if (isset($this->value[$key])) {
      $elements[$key] = $this
        ->parseElement($key, $this->value[$key], $definition);
    }
  }
  return $elements;
}