def my_private_tag(value, arg):
  return value + ' ' + arg

{% if name %}

  # to display
  # John says hello
  {{name.first | my_private_tag:"says hello"}

  # Johns student id = id_value
  {{name.first | my_private_tag:"????????"}

  # Johns student id = id_value, lastname = lastname_value
  {{name.first | my_private_tag:"????????"}

{% endif %}

id_value = name.id & lastname_value = name.last

{{name.first }} says hello
{{name.first }}'s student id = {{ name.id }}

{{name.first|my_private_tag:name.id}}

Johns student id = 47, lastname = Doe

{{name|my_private_tag:"??????"}}

return name.first_name + "s student id = " + name.id + ", lastname = " + name.last_name