@abc.abstractmethod<EOL><INDENT>def get_string_match_types(self):<DEDENT>
return<EOL>
Gets the set of valid string match types for use in validating a string.

        If the string match type indicates a regular expression then
        ``get_string_expression()`` returns a regular expression.

        :return: the set of string match types
        :rtype: ``osid.type.Type``
        :raise: ``IllegalState`` -- syntax is not a ``STRING``

        *compliance: mandatory -- This method must be implemented.*