Trouble with optional fields in Struct.pick function

interface Foo {
  createdAt: number;
  pmName?: string;
  issuerName: string;
}

const foo: Foo = {
  createdAt: 123432412,
  pmName: "pmName",
  issuerName: "issuerName",
};
const fooBar = (foo: Foo): Partial<Foo> => {
  return F.pipe(foo, Struct.pick("pmName", "issuerName"));
}