docs: def to_dict(self):
          """Convert a SON document to a normal Python dictionary instance.
  
          This is trickier than just *dict(...)* because it needs to be
          recursive.
          """
  
          def transform_value(value):
              if isinstance(value, list):
                  return [transform_value(v) for v in value]
              elif isinstance(value, collections.Mapping):
                  return dict([
                      (k, transform_value(v))
                      for k, v in iteritems(value)])
              else:
                  return value
  
          return transform_value(dict(self))