def expand(self, expression):
    """pass"""
    self.logger.debug('expand : expression %s', str(expression))
    if not is_string(expression):
        return expression
    result = self._pattern.sub(lambda var: str(self._variables[var.group(1)]), expression)
    result = result.strip()
    self.logger.debug('expand : %s - result : %s', expression, result)
    if is_number(result):
        if result.isdigit():
            self.logger.debug('     expand is integer !!!')
            return int(result)
        else:
            self.logger.debug('     expand is float !!!')
            return float(result)
    return result