Convert an individual value to an XML string. Calls itself
    recursively for dictionaries and lists.

    Uses some heuristics to convert the data to XML:
        - In dictionaries, the keys become the tag name.
        - In lists the tag name is 'child' with an order-attribute giving
          the list index.
        - All other values are included as is.

    All values are escaped to fit into the XML document.

    :param value: The value to convert to XML.
    :type value: Any valid Python value
    :rtype: string

def _get_xml_value(value):
    """Convert an individual value to an XML string. Calls itself
    recursively for dictionaries and lists.

    Uses some heuristics to convert the data to XML:
        - In dictionaries, the keys become the tag name.
        - In lists the tag name is 'child' with an order-attribute giving
          the list index.
        - All other values are included as is.

    All values are escaped to fit into the XML document.

    :param value: The value to convert to XML.
    :type value: Any valid Python value
    :rtype: string
    """
    retval = []
    if isinstance(value, dict):
        for key, value in value.iteritems():
            retval.append('<' + xml_escape(str(key)) + '>')
            retval.append(_get_xml_value(value))
            retval.append('</' + xml_escape(str(key)) + '>')
    elif isinstance(value, list):
        for key, value in enumerate(value):
            retval.append('<child order="' + xml_escape(str(key)) + '">')
            retval.append(_get_xml_value(value))
            retval.append('</child>')
    elif isinstance(value, bool):
        retval.append(xml_escape(str(value).lower()))
    elif isinstance(value, unicode):
        retval.append(xml_escape(value.encode('utf-8')))
    else:
        retval.append(xml_escape(str(value)))
    return "".join(retval)