Get minimum of SortedKeyList with a condition on an object attribute

I have a SortedKeyList of objects sorted by timestamp, the objects also have another attribute, the ID.

I was trying to get the earliest element of the list based on the ID.

This is a code example:

import numpy as np
import sortedcontainers

class Point:
    def __init__(self, timestamp, id):
        self.timestamp = timestamp
        self.id = id

point_list = sortedcontainers.SortedKeyList(key=lambda x: x.timestamp)

point_list.add(Point(np.datetime64("2021-07-05T09:00:00"), "B"))
point_list.add(Point(np.datetime64("2021-07-05T09:00:01"), "A"))
point_list.add(Point(np.datetime64("2021-07-05T09:00:03"), "A"))
point_list.add(Point(np.datetime64("2021-07-05T09:01:00"), "B"))

I would like to select on the ID and take the minimum.

For example I want the earliest point for ID=A and, in this case, is:

Point(np.datetime64("2021-07-05T09:00:01"), "A")

I was trying to do something like this:

min(point_list, key=lambda x: x.timestamp if(x.id=="A") else None).timestamp

but this give me a TypeError:

TypeError: '<' not supported between instances of 'datetime.datetime' and 'NoneType'

This is part of a bigger project, so I can refactor the part related to SortedKeyList, but I can't modify the object Point.

Any idea?

Following @hpaulj I used a late np.datetime64:

min(point_list, key=lambda x: x.timestamp if(x.id=="A") else np.datetime64("now").astype("datetime64[ns]")).timestamp

as the time precision over the other timestamp is in nanoseconds, I am pretty confident that this should be fine.