docs: def set_namespace(namespace, attribute, namespace_splitter=NAMESPACE_SPLITTER):
      """
      Sets given namespace to given attribute.
  
      Usage::
  
          >>> set_namespace("parent", "child")
          u'parent|child'
  
      :param namespace: Namespace.
      :type namespace: unicode
      :param attribute: Attribute.
      :type attribute: unicode
      :param namespace_splitter: Namespace splitter character.
      :type namespace_splitter: unicode
      :return: Namespaced attribute.
      :rtype: unicode
      """
  
      long_name = "{0}{1}{2}".format(namespace, namespace_splitter, attribute)
      LOGGER.debug("> Namespace: '{0}', attribute: '{1}', long name: '{2}'.".format(namespace, attribute, long_name))
      return long_name