docs: def build_model_classes(metadata):
      """Generate a model class for any models contained in the specified spec file."""
      i = importlib.import_module(metadata)
      env = get_jinja_env()
      model_template = env.get_template('model.py.jinja2')
      for model in i.models:
          with open(model_path(model.name.lower()), 'w') as t:
              t.write(model_template.render(model_md=model))