class Aws::Stubbing::EmptyStub

def stub_ref(ref, visited = [])
  if visited.include?(ref.shape)
    return nil
  else
    visited = visited + [ref.shape]
  end
  case ref.shape
  when StructureShape then stub_structure(ref, visited)
  when ListShape then []
  when MapShape then {}
  else stub_scalar(ref)
  end
end