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

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