Function flatten

flatten(obj, propsRecursive?, ...props): Record<string, any>
Flatten an object. Any properties that are collections will get converted to an array of keys.
Parameters
- obj: Record<string, any>
  The object to flatten.
- OptionalpropsRecursive: boolean
  Optional. If true, calls toJSON method on nested objects.
- Rest...props: Record<string, string | boolean>[]
  Optional. Specific properties to include/exclude, or rename.
Returns Record<string, any>
Flattened object.