setdefault(key, default=None)
  If key is in the ParameterDict, return its value. If not, insert
  *key* with a parameter *default* and return *default*. *default*
  defaults to *None*.

  Parameters:
     * **key** (*str*) -- key to set default for

     * **default** (*Any*) -- the parameter set to the key

  Return type:
     *Any*

update(parameters)
  Update the "ParameterDict" with the key-value pairs from a
  mapping or an iterable, overwriting existing keys.

  Note:

    If "parameters" is an "OrderedDict", a "ParameterDict", or an
    iterable of key-value pairs, the order of new elements in it
    is preserved.

  Parameters:
     **parameters** (*iterable*) -- a mapping (dictionary) from
     string to "Parameter", or an iterable of key-value pairs of
     type (string, "Parameter")

values()
  Return an iterable of the ParameterDict values.

  Return type:
     *Iterable*[*Any*]
