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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 get(self, filename):
 """ Check if a distribution archive exists in the local cache. :param filename: The filename of the distribution archive (a string). :returns: The pathname of a distribution archive on the local file system or :data:`None`. """

        pathname = os.path.join(self.config.binary_cache, filename)
        if os.path.isfile(pathname):
            logger.debug("Distribution archive exists in local cache (%s).", pathname)
            return pathname
        else:
            logger.debug("Distribution archive doesn't exist in local cache (%s).", pathname)
            return None