Return the text value of an xml element node. Leading and trailing
           whitespace is stripped from the value unless the preserve_ws flag
           is passed with a true value.

def getElementText(self, node, preserve_ws=None):
        """Return the text value of an xml element node. Leading and trailing
           whitespace is stripped from the value unless the preserve_ws flag
           is passed with a true value."""
        result = []
        for child in node.childNodes:
            nodetype = child.nodeType
            if nodetype == child.TEXT_NODE or \
               nodetype == child.CDATA_SECTION_NODE:
                result.append(child.nodeValue)
        value = join(result, '')
        if preserve_ws is None:
            value = strip(value)
        return value