Update type and typestring lookup dicts.

        Must be called once the ``types`` and ``python_type_strings``
        attributes are set so that ``type_to_typestring`` and
        ``typestring_to_type`` are constructed.

        .. versionadded:: 0.2

        Notes
        -----
        Subclasses need to call this function explicitly.

def update_type_lookups(self):
        """ Update type and typestring lookup dicts.

        Must be called once the ``types`` and ``python_type_strings``
        attributes are set so that ``type_to_typestring`` and
        ``typestring_to_type`` are constructed.

        .. versionadded:: 0.2

        Notes
        -----
        Subclasses need to call this function explicitly.

        """
        self.type_to_typestring = dict(zip(self.types,
                                           self.python_type_strings))
        self.typestring_to_type = dict(zip(self.python_type_strings,
                                           self.types))