'Constructor.
:param simple_dags: SimpleDag objects that should be in this
:type: list(SimpleDag)'

def __init__(self, simple_dags):

    self.simple_dags = simple_dags
    self.dag_id_to_simple_dag = {}
    for simple_dag in simple_dags:
        self.dag_id_to_simple_dag[simple_dag.dag_id] = simple_dag
