'Provides the indexable - search engine oriented - raw text
@param tree: an ElementTree
@return: set(["foo", "bar", ...])'

def indexableText(self, tree):

    rval = set()
    root = tree.getroot()
    for txp in self.text_elts_xpaths:
        elts = txp(root)
        texts = []
        for elt in elts:
            text = self.text_extract_xpath(elt)
            if (len(text) > 0):
                texts.append(text[0])
        texts = self.separator.join(texts)
        texts = [toUnicode(x) for x in self.wordssearch_rx.findall(texts) if (len(x) > 0)]
        rval |= set(texts)
    return rval
