Have recently started to use Airflow for various jobs, trying to get handle on templating.

I was very impressed by EmailOperator, in which you could specify a html_content to be a HTML file, which would then be able to access variables from eg. ti.xcom_pull and put them in proper template places.

I am trying to do something similar with XML template that needs to be saved to file, but the question is how and at which point I should pass params variable to the rendering, if I want to have the data in that variable available to xml_file template during rendering, eg. via {{ params.xyz }} ?

class CreateXMLFromTemplate(BaseOperator):
    template_fields = ('xml_file')
    template_ext = ('.xml','.html')

    def __init__(
    self,
    *,
    xml_file,
    params,
    output_file,
    **kwargs,
    ):
        super().__init__(**kwargs)
        self.xml_file=xml_file
        self.params=params
        self.output_file=output_file
    
    def execute(self,context):
        with open(self.output_file,'w') as F:
            F.write(self.xml_file) #<- this has rendered airflow builtin templates ok already
        return self.output_file

However, as the rendering is automatic somewhere in BaseOperator, it is not clear, how should I go about having the XML rendered output to be able to take in parameters specified in params variable.