OpenAPI -> TypeScript adds wildcard prop to each type

I'm using typeconv to convert some OpenAPI schemas into TypeScript interfaces. Generally working great, but I noticed one thing.

When I start with the below OpenAPI spec:

```js
{
components: {
schemas: {
Person: {
type: "object",
properties: {
first_name: {
type: "string",
example: "Pam",
},
last_name: {
type: "string",
example: "Halpert",
},
},
required: [],
title: "Person",
},
},
},
};
```

It produces the following type:

```ts
export interface Person {
first_name?: string;
last_name?: string;
[key: string]: any;
}
```

Almost perfect, except for that last line:

```ts
[key: string]: any;
```

It's appending a wildcard accessor to my type, for some reason, essentially asserting that on `Person`, any string can access any value, which makes the type not particularly helpful.

Any ideas what this is happening? I could get rid of this line through string manipulation, but I wonder why it's happening, and if there's some option I'm missing.