def get_value_record(self, value_record_type=None):
Gets the value record corresponding to the given ``Value`` record ``Type``.

        This method is used to retrieve an object implementing the
        requested record. The ``value_record_type`` may be the ``Type``
        returned in ``get_record_types()`` or any of its parents in a
        ``Type`` hierarchy where ``has_record_type(value_record_type)``
        is ``true`` .

        arg:    value_record_type (osid.type.Type): the type of value
                record to retrieve
        return: (osid.configuration.records.ValueRecord) - the value
                record
        raise:  NullArgument - ``value_record_type`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unsupported - ``has_record_type(value_record_type)`` is
                ``false``
        *compliance: mandatory -- This method must be implemented.*