Map the function f to the nested structure x (dicts, tuples, lists).

def nested_map(x, f):
  """Map the function f to the nested structure x (dicts, tuples, lists)."""
  if isinstance(x, list):
    return [nested_map(y, f) for y in x]
  if isinstance(x, tuple):
    return tuple([nested_map(y, f) for y in x])
  if isinstance(x, dict):
    return {k: nested_map(x[k], f) for k in x}
  return f(x)