def keys(self, key_type=None):
if key_type is not None:<EOL><INDENT>intermediate_key = str(key_type)<EOL>if intermediate_key in self.__dict__:<EOL><INDENT>return self.__dict__[intermediate_key].keys()<EOL><DEDENT><DEDENT>else:<EOL><INDENT>all_keys = {} <EOL>for keys in self.items_dict.keys():<EOL><INDENT>all_keys[keys] = None<EOL><DEDENT>return all_keys.keys()<EOL><DEDENT>
Returns a copy of the dictionary's keys.
            @param key_type if specified, only keys for this type will be returned.
                 Otherwise list of tuples containing all (multiple) keys will be returned.