def extract_relationtypes(rs3_xml_tree):
    """
    extracts the allowed RST relation names and relation types from
    an RS3 XML file.

    Parameters
    ----------
    rs3_xml_tree : lxml.etree._ElementTree
        lxml ElementTree representation of an RS3 XML file

    Returns
    -------
    relations : dict of (str, str)
        Returns a dictionary with RST relation names as keys (str)
        and relation types (either 'rst' or 'multinuc') as values
        (str).
    """
    return {rel.attrib['name']: rel.attrib['type']
            for rel in rs3_xml_tree.iter('rel')
            if 'type' in rel.attrib}