'Return the data in this field or \'\' if the field is empty'

def __get__(self, obj, typ=None):

    document = obj.info
    elems = document.getElementsByTagName(self.tag_name)
    if len(elems):
        elem = None
        for candidate in elems:
            if (candidate.parentNode.nodeName == self.parent):
                elem = candidate
        if (elem and elem.hasAttribute(self.attr)):
            return elem.getAttribute(self.attr)
    return ''
