'Get an lxml etree if possible.'

def lxml(self):

    if (('html' not in self.mimetype) and ('xml' not in self.mimetype)):
        raise AttributeError('Not    an    HTML/XML    response')
    from lxml import etree
    try:
        from lxml.html import fromstring
    except ImportError:
        fromstring = etree.HTML
    if (self.mimetype == 'text/html'):
        return fromstring(self.data)
    return etree.XML(self.data)
