def schedule_to_proto_dicts(schedule: Schedule) -> Iterable[Dict]:
    """Convert a schedule into an iterable of proto dictionaries.

    Args:
        schedule: The schedule to convert to a proto dict. Must contain only
            gates that can be cast to xmon gates.

    Yields:
        A proto dictionary corresponding to an Operation proto.
    """
    last_time_picos = None  # type: Optional[int]
    for so in schedule.scheduled_operations:
        op = gate_to_proto_dict(
            cast(ops.GateOperation, so.operation).gate,
            so.operation.qubits)
        time_picos = so.time.raw_picos()
        if last_time_picos is None:
            op['incremental_delay_picoseconds'] = time_picos
        else:
            op['incremental_delay_picoseconds'] = time_picos - last_time_picos
        last_time_picos = time_picos
        yield op