Patterns with fields with privacy policies generate invalid JS

[Swahvay]

If a pattern has a struct field with a privacy policy, the type that is specified in the return of the check function is missing in the import list. I.e.:

export const SomePattern: Pattern = {
  name: 'SomePattern',
  fields: {
    someEnumField: StructTypeAsList({
      tsType: 'SomeEnumField',
      nullable: true,
      privacyPolicy: {
        rules: [AlwaysDenyRule],
      },
      fields: {
        a: BooleanType(),
        b: StringType(),
      },
    }),
  },
};

Generates the following in each base class:

async someEnumFields(): Promise<SomeEnumField[] | null> {
  if (this._someEnumField === null) {
    return null;
  }
  // etc.
}

But SomeEnumField is never imported so we get TS build errors.

[Swahvay]

The offending line: base.tmpl#L186. Unfortunately I don't know enough about Go templating to know how to import that file appropriately.