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

:type  wf_spec: WorkflowSpec
:param wf_spec: A reference to the workflow specification.
:type  name: str
:param name: The name of the task spec.
:type  mutex: str
:param mutex: The name of the mutex that should be acquired.
:type  kwargs: dict
:param kwargs: See :class:`SpiffWorkflow.specs.TaskSpec`.