def used_expectations_files(self):
        """Returns a list of paths to expectation files that are used."""
        if self._used_expectation_files is None:
            self._used_expectation_files = list(
                self.default_expectations_files())
            flag_specific = self._flag_specific_expectations_path()
            if flag_specific:
                self._used_expectation_files.append(flag_specific)
            for path in self.get_option('additional_expectations', []):
                expanded_path = self._filesystem.expanduser(path)
                abs_path = self._filesystem.abspath(expanded_path)
                self._used_expectation_files.append(abs_path)
        return self._used_expectation_files