Object additionalProperties incorrect with anyOf

I am trying to define a schema mapping to `Record` with the following schema snippet:

```ts
type: object
additionalDetails:
type: object
description: Additional properties
additionalProperties:
anyOf:
- type: string
- type: number
- type: array
items:
type: string
```

However swagger-typescript-api seems to be ignoring `anyOf` and is just generating a signature based on the last element in the array, rather than generating a union of the listed types.

```ts
additionalDetails?: Record;
```