'GET /api/workflows/{workflow_id}/invocations
Get the list of the workflow invocations
:param  workflow_id:      the workflow id (required)
:type   workflow_id:      str
:raises: exceptions.MessageException, exceptions.ObjectNotFound'

@expose_api
def index_invocations(self, trans, workflow_id, **kwd):

    stored_workflow = self.__get_stored_workflow(trans, workflow_id)
    results = self.workflow_manager.build_invocations_query(trans, stored_workflow.id)
    out = []
    for r in results:
        out.append(self.__encode_invocation(trans, r, view='collection'))
    return out
