(init-state params ..body)
  params: an arr
  body: zero or more forms

Defines a state initializer method.

After a state is enabled using enab!, its initializer method is automatically invoked with the given arguments.

When a state is automatically enabled (for example, because it was defined using a state* clause), its initializer method will be invoked without any arguments.

@-parameters are supported, exactly as for an init clause.