Expanding Jinja within Jsonnet via Python bindings

test.jsonnet

local expand_template(template, vars) =
    std.native("expand_template")(template, std.toString(vars));


{
    response: expand_template(|||
        Hello {{ title }} {{ family_name }}, please take a seat.
    |||, {
        title: "Dr",
        family_name: "Frankenstein",
    }),
}

test.py

import jinja2
import json
import _jsonnet
import sys

def expand_template(template, env_json):
    env = json.loads(env_json)
    r = jinja2.Environment().from_string(template).render(**env)
    return r.encode('utf8')

native_callbacks = {
    'expand_template': (('template', 'env_json'), expand_template),
}   

json_str = _jsonnet.evaluate_file(
    'test.jsonnet',
    native_callbacks=native_callbacks,
)   
sys.stdout.write(json_str)