'Required:
att -- the attribute
value -- the value
Returns:
nothing
Logic:
Try to add the attribute value directly to the styles dictionary.
If a keyerror is found, that means I have to build the "branches"
of the dictionary before I can add the key value pair.'

def __enter_dict_entry(self, att, value):

    try:
        self.__styles_dict[self.__type_of_style][self.__styles_num][att] = value
    except KeyError:
        self.__add_dict_entry(att, value)
