Start thread to render a given documentation

def render(self, doc, context=None, math_option=False, img_path='',
               css_path=CSS_PATH):
        """Start thread to render a given documentation"""
        # If the thread is already running wait for it to finish before
        # starting it again.
        if self.wait():
            self.doc = doc
            self.context = context
            self.math_option = math_option
            self.img_path = img_path
            self.css_path = css_path
            # This causes run() to be executed in separate thread
            self.start()