def _unify_values(self, section, vars):
        """Create a sequence of lookups with 'vars' taking priority over
        the 'section' which takes priority over the DEFAULTSECT.

        """
        sectiondict = {}
        try:
            sectiondict = self._sections[section]
        except KeyError:
            if section != self.default_section:
                raise NoSectionError(section)
        # Update with the entry specific variables
        vardict = {}
        if vars:
            for key, value in vars.items():
                if value is not None:
                    value = str(value)
                vardict[self.optionxform(key)] = value
        return _ChainMap(vardict, sectiondict, self._defaults)