Allow SerializerMethodField fields to return nested iterables

[AntonioDell]

In our project we have the need to create typescript interfaces for complex serializers, which include the following:

class MeteringPointSerializer(serializers.ModelSerializer):
    # some fields...

    vacancy_time_slices = serializers.SerializerMethodField()

    def get_vacancy_time_slices(self, instance) -> List[Tuple[date, date]]:
        # some implementation returning a list of tuples....

    # rest of the serializer

Trying to create typescript interface for this serializer results in the following error:

Traceback (most recent call last):
  File "/workspace/api/app/./manage_debug.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/workspace/api/.venv/lib/python3.11/site-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
    utility.execute()
  File "/workspace/api/.venv/lib/python3.11/site-packages/django/core/management/__init__.py", line 413, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/workspace/api/.venv/lib/python3.11/site-packages/django/core/management/base.py", line 354, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/workspace/api/.venv/lib/python3.11/site-packages/django/core/management/base.py", line 398, in execute
    output = self.handle(*args, **options)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/management/commands/generate_ts.py", line 147, in handle
    self._generate_ts(app_name, serializer_name, output, **options)
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/management/commands/generate_ts.py", line 114, in _generate_ts
    generate_ts(
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/__init__.py", line 513, in generate_ts
    interfaces_enums = __generate_interfaces_and_enums(
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/__init__.py", line 416, in __generate_interfaces_and_enums
    return [
           ^
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/__init__.py", line 417, in <listcomp>
    __get_ts_interface_and_enums(
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/__init__.py", line 373, in __get_ts_interface_and_enums
    ts_property, ts_type, ts_enum, ts_enum_value = __process_field(
                                                   ^^^^^^^^^^^^^^^^
  File "/workspace/api/.venv/lib/python3.11/site-packages/django_typomatic/__init__.py", line 248, in __process_field
    if issubclass(return_type, BaseSerializer):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: issubclass() arg 1 must be a class

After some debugging I discovered, that it was because of the TODO comments topic of allowing nested iterables.

It would be awesome to have support for this.

[markolofsen]

Unfortunately I got same problem =)