pb with frame name in lookup_transform

Question

I've done the tutorial for tf2, and everything works fine. Now I'm trying to reproduce the "follow" behavior with drones, but this time it fails. I've got a Node for each drone. I do the broadcast exactly like in the tutorial and it works. At least I can see the transformation with ros2 run tf2_ros tf2_echo cis_drone_2 cis_drone_1

At time 1693834924.724220138
- Translation: [1.000, 1.000, 0.000]
- Rotation: in Quaternion [0.000, -0.000, -0.000, 1.000]
- Rotation: in RPY (radian) [0.000, -0.000, -0.000]
- Rotation: in RPY (degree) [0.000, -0.000, -0.000]
- Matrix:
  1.000  0.000 -0.000  1.000
 -0.000  1.000 -0.000  1.000
  0.000  0.000  1.000  0.000
  0.000  0.000  0.000  1.000

This is on startup, both drones are on the floor. Then I start the "follow action" building the TransformListener once again like in the tutorial. Here is my callback

# frames involved
from_frame = self._leader
to_frame = self.name

# Look up for the transformation between leader_frame and this mobile frame
try:
    t = self.__buffer.lookup_transform(
        to_frame,
        from_frame,
        rclpy.time.Time(),
        timeout=rclpy.duration.Duration(seconds=3.0),
    )
except TransformException as ex:
    self.get_logger().info(
        f'Could not transform {to_frame} to {from_frame}: {ex}')
    return
self.get_logger().info(f"Transform is {t}")

Here I get an exception :

Could not transform cis_drone_2 to cis_drone_1: "cis_drone_2" passed to lookupTransform argument target_frame does not exist.

And in the terminal running tf2_echo I get this error :

Failure at 1693834935.374
Exception thrown:Lookup would require extrapolation into the past.  Requested time 1693834924.724220 but the earliest data is at time 1693834925.739769, when looking up transform from frame [cis_drone_1] to frame [cis_drone_2]
The current list of frames is:
Frame cis_drone_1 exists with parent warehouse_lanes.
Frame cis_drone_2 exists with parent warehouse_lanes.

I tried to use 0 as a value for time in lookup_transform, doc says it will get the latest, but I get this new error

[drone-11]   File "/opt/ros/humble/lib/python3.10/site-packages/tf2_ros/buffer.py", line 135, in lookup_transform
[drone-11]     self.can_transform(target_frame, source_frame, time, timeout)
[drone-11]   File "/opt/ros/humble/lib/python3.10/site-packages/tf2_ros/buffer.py", line 221, in can_transform
[drone-11]     not self.can_transform_core(target_frame, source_frame, time)[0] and
[drone-11] TypeError: time must have sec and nanosec, or nanoseconds.

Do I have to use the "traveling in time" to perform this "immediate" follow ?