<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def load_suite_from_file(self, filename):
 """Load a test suite with test lines from the provided TAP file. :returns: A ``unittest.TestSuite`` instance """

        suite = unittest.TestSuite()
        rules = Rules(filename, suite)

        if not os.path.exists(filename):
            rules.handle_file_does_not_exist()
            return suite

        line_generator = self._parser.parse_file(filename)
        return self._load_lines(filename, line_generator, suite, rules)