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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def grab_definition(self, url):
 """ Grab the column definition of a table from the EPA using a combination of regular expressions and lxml. """

        re_description = re.compile('Description:(.+?\\n)')
        re_table_name = re.compile("(\w+ Table.+)")
        if url.startswith('//'):
            url = 'http:' + url
        elif url.startswith('/'):
            url = 'http://www.epa.gov' + url
        try:
            html = urlopen(url).read()
            doc = lh.fromstring(html)
            main = doc.cssselect('#main')[0]
            text = main.text_content()
            definition = re_description.search(text).group(1).strip()
        except (AttributeError, IndexError, TypeError, HTTPError):
            print url
        else:
            value = re_table_name.sub('', definition)
            return value
        return url