How to use the cssselect.xpath function in cssselect

#-*- coding:utf-8 -*-
#
# Copyright (C) 2008 - Olivier Lauzanne 
#
# Distributed under the BSD license, see LICENSE.txt
from cssselect import xpath as cssselect_xpath


class PDFQueryTranslator(cssselect_xpath.GenericTranslator):

    def xpath_in_bbox_function(self, xpath, fn):
        if len(fn.arguments) > 1:
            x0,y0,x1,y1 = [float(t.value) for t in fn.arguments]
        else:
            x0,y0,x1,y1 = map(float, fn.arguments[0].value.split(","))
        # TODO: seems to be doing < rather than <= ???
        xpath.add_condition("@x0 >= %s" % x0)
        xpath.add_condition("@y0 >= %s" % y0)
        xpath.add_condition("@x1 <= %s" % x1)
        xpath.add_condition("@y1 <= %s" % y1)
        return xpath

    def xpath_overlaps_bbox_function(self, xpath, fn):
        if len(fn.arguments) > 1:
            x0,y0,x1,y1 = [float(t.value) for t in fn.arguments]

# Copyright (C) 2008 - Olivier Lauzanne 
#
# Distributed under the BSD license, see LICENSE.txt
from __future__ import unicode_literals
from cssselect import xpath as cssselect_xpath
from cssselect.xpath import ExpressionError

XPathExprOrig = cssselect_xpath.XPathExpr


class XPathExpr(XPathExprOrig):

    def __init__(self, path='', element='*', condition='', star_prefix=False):
        self.path = path
        self.element = element
        self.condition = condition
        self.post_condition = None

    def add_post_condition(self, post_condition):
        if self.post_condition:
            self.post_condition = '%s and (%s)' % (self.post_condition,
                                                   post_condition)
        else:
            self.post_condition = post_condition

def __str__(self):
        path = XPathExprOrig.__str__(self)
        if self.post_condition:
            path = '%s[%s]' % (path, self.post_condition)
        return path

    def join(self, combiner, other):
        res = XPathExprOrig.join(self, combiner, other)
        self.post_condition = other.post_condition
        return res


# keep cssselect < 0.8 compat for now


class JQueryTranslator(cssselect_xpath.HTMLTranslator):
    """This class is used to implement the css pseudo classes
    (:first, :last, ...) that are not defined in the css standard,
    but are defined in the jquery API.
    """

    xpathexpr_cls = XPathExpr

    def xpath_first_pseudo(self, xpath):
        """Matches the first selected element::

            >>> from pyquery import PyQuery
            &gt;&gt;&gt; d = PyQuery('<div><p class="first"></p><p></p></div>')
            &gt;&gt;&gt; d('p:first')
            []

        ..