human
Complete the below
def lead_text(top_elem, num_words=10):

    ''''Return the leading text contained in top_elem (including descendants)
    up to a maximum of num_words words. More efficient than using
    etree.tostring(method=\'text\') as it does not have to serialize the entire
    sub-tree rooted at top_elem.'
    '''
 ... Write me a the Python program you requested?
assistant
#Here is the Python program you requested.
    pat = re.compile(u'\\s+', flags=re.UNICODE)
    words = []
    def get_text(x, attr=u'text'):
        ans = getattr(x, attr)
        if ans:
            words.extend(filter(None, pat.split(ans)))
    stack = [(top_elem, u'text')]
    while (stack and (len(words) < num_words)):
        (elem, attr) = stack.pop()
        get_text(elem, attr)
        if (attr == u'text'):
            if (elem is not top_elem):
                stack.append((elem, u'tail'))
            stack.extend(reversed(list(((c, u'text') for c in elem.iterchildren(u'*')))))
    return u'    '.join(words[:num_words])