[Feature request] Add independent depart for Flow

[qianyi-sun]

Proposal

The desired pseudo code could be like:

class Flow:
...
    depart: float = 0
    """"Start time in seconds"""

Motivation

Currently depart only available in Trip class and if we set depart for a Traffic(flows=[Flow(...)], trips=[Trip(....,depart=...)]), seems like the depart doesnt only affect the trips but also affect the flows as well.

Sometimes we want the flows go first for several seconds to make sure there's some traffic prior to the trip actor, especially for the following scenarios, as we use trip actor as the leader. Therefore we might need a seperate depart for the flows so that we could control the depart time for flows and trip actor seperately.

Alternatives

No response

Additional context

No response