helpers.d.ts

type Diff<
  T extends string | number | symbol,
  U extends string | number | symbol
> = ({[P in T]: P} & {[P in U]: never} & {[x: string]: never})[T]

export type Omit<T, K extends keyof T> = Pick<T, Diff<keyof T, K>>

export type SingleOrArray<Properties, T extends keyof Properties> = {
  [P in T]: Properties[P] | Array<Properties[P]>
}