Makes sure the table with the full name comprising of name_seq exists.

def _make_sure_table_exists(self, name_seq):
        """
        Makes sure the table with the full name comprising of name_seq exists.
        """
        t = self
        for key in name_seq[:-1]:
            t = t[key]
        name = name_seq[-1]
        if name not in t:
            self.append_elements([element_factory.create_table_header_element(name_seq),
                                  element_factory.create_table({})])