def time_zone_by_country_and_region(country_code, region_code=None):
timezone = country_dict.get(country_code)<EOL>if not timezone:<EOL><INDENT>return None<EOL><DEDENT>if isinstance(timezone, str):<EOL><INDENT>return timezone<EOL><DEDENT>return timezone.get(region_code)<EOL>
Returns time zone from country and region code.

:arg country_code: Country code
:arg region_code: Region code