Foo = ref object of RootObj
  ...
proc baz(this: Foo, arg: string) = do_something_with_foo(arg)

Bar = ref object of RootObj
  _items: Table[string, Foo]  # _items is private member
  ...
proc items(this: Bar): Table[string, Foo] = this._items
# Now, I want to use this
var b = newBar() # _items populated
b.items["key"].baz("some argument")
# How to do this ?
# Compiler says
 Error: type mismatch
Expression: `[]`(items(b), "key")
  [1] items(b): Table[system.string, Foo]
  [2] "key": string

Expected one of (first mismatch at [position]):
[0] proc `[]`(s: string; i: BackwardsIndex): char
[0] proc `[]`(s: var string; i: BackwardsIndex): var char
[0] proc `[]`[I: Ordinal; T](a: T; i: I): T
[0] proc `[]`[Idx, T; U, V: Ordinal](a: array[Idx, T]; x: HSlice[U, V]): seq[T]
[0] proc `[]`[Idx, T](a: array[Idx, T]; i: BackwardsIndex): T
[0] proc `[]`[Idx, T](a: var array[Idx, T]; i: BackwardsIndex): var T
[0] proc `[]`[T, U: Ordinal](s: string; x: HSlice[T, U]): string
[0] proc `[]`[T; U, V: Ordinal](s: openArray[T]; x: HSlice[U, V]): seq[T]
[0] proc `[]`[T](s: openArray[T]; i: BackwardsIndex): T
[0] proc `[]`[T](s: var openArray[T]; i: BackwardsIndex): var T
[0] template `[]`(s: string; i: int): char