Write a function named is_sub_dict that accepts two dictionaries from strings to strings as its parameters and returns True if every key in the first dictionary is also contained in the second dictionary and maps to the same value in the second dictionary. For example, given the dictionaries below, map1 is a sub-dict of map2, so the call of is_sub_dict(map1, map2) would return True. The order of the parameters does matter, so the call of is_sub_dict(map2, map1) would return False.