def render_template_string(self, plain, rich = None, **context):
self.plain = render_template_string(plain, **context)<EOL>if rich is not None:<EOL><INDENT>self.rich = render_template_string(rich, **context)<EOL><DEDENT>
Render the body of the message from a string. If ``rich`` isn’t 
        provided then the message will not have a rich body.