option : any Hashable object
An option that is required for the decorated method to execute.
This option will be looked up within the containing Workflow``s'
``options .
values : object
A required value. This defaults to anything indicating that
the only requirement is that the option exists. It can be
useful to specify not_none which indicates that the
requirement is satisfied if the option exists and it holds
a value that is not None . Values also supports iterables
or singular values.
state : Function
A requirement on workflow state. This must be a function that
accepts a single argument, and returns True to indicate
the requirement is satisfied, or False to indicate the
requirement is not satisfied. This method will be passed the
containing Workflow``s' ``state member variable.
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