(gdb) python
>class mynewparameter(gdb.Parameter):
>#  "01234567890123456789"
>  def __init__(self):
>#    self.set_doc="01234567890123456789"
>    self.show_doc="01234567890123456789"
>    super(mynewparameter, self).__init__('mynewparameter',
>         gdb.COMMAND_DATA, gdb.PARAM_UINTEGER)
>    self.value = 20
>mynewparameter()
>end
(gdb) show mynewparameter
567890123456789 is 20.
(gdb) help set mynewparameter
This command is not documented.
This command is not documented.

- for show_doc the first 5 character are skipped
- "help set parameter-name" evaluates both: the set_doc and the __doc__ string. If it is not set, "This command is not documented." appears - otherwise the corresponding string is printed. 


For c&p:

python
class mynewparameter(gdb.Parameter):
  "01234567890123456789"
  def __init__(self):
    self.set_doc="01234567890123456789"
    self.show_doc="01234567890123456789"
    super(mynewparameter, self).__init__('mynewparameter',
         gdb.COMMAND_DATA, gdb.PARAM_UINTEGER)
    self.value = 20
mynewparameter()
end
show mynewparameter
help set mynewparameter