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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def set_topological_dag_upstreams(dag, ops, op_runs, runs_by_ops):
 """Set the upstream runs for the operation runs in the dag following the topological sort."""

    sorted_ops = dags.sort_topologically(dag=dag)
    for op_id in sorted_ops:
        op_run_id = runs_by_ops[op_id]
        op_run = op_runs[op_run_id]
        set_op_upstreams(op_run=op_run, op=ops[op_id])