def __init__(self,<EOL>wf_spec,<EOL>name,<EOL>split_task,<EOL>**kwargs):
assert split_task is not None<EOL>Join.__init__(self, wf_spec, name, split_task, **kwargs)<EOL>
Constructor.

:type  wf_spec: :class:`SpiffWorkflow.specs.WorkflowSpec`
:param wf_spec: A reference to the parent (usually a workflow).
:type  name: string
:param name: A name for the task.
:type  split_task: str
:param split_task: The name of the task spec that was previously
                   used to split the branch.
:type  kwargs: dict
:param kwargs: See :class:`SpiffWorkflow.specs.Join`.