@on_by_default.setter<EOL><INDENT>def on_by_default(self, on_by_default):<DEDENT>
self._on_by_default = on_by_default<EOL>
Sets the on_by_default of this V1ModifierOption.
If true, the modifier option is the default option in a modifier list for which selection_type is SINGLE.

:param on_by_default: The on_by_default of this V1ModifierOption.
:type: bool