Add a snippet to verify the new sample data can be fetched

[sfmig]

Is your feature request related to a problem? Please describe. It could be nice to add a quick snippet in the adding data section, to see if your sample data file can be fetched.

Describe the solution you'd like For example, for the zebras dataset that looks like:

from movement import sample_data
from movement.io import load_poses

file_path = sample_data.fetch_dataset_paths("SLEAP_OSFM_zebras_drone.h5")["poses"]
ds = load_poses.from_sleap_file(file_path)
print(ds)

Describe alternatives you've considered \

Additional context I tend to do this if I upload a file that is not for testing, maybe others find it useful.

[sfmig]

Or alternatively:

ds = sample_data.fetch_dataset("SLEAP_OSFM_zebras_drone.h5")

Note that not all datasets are meant to be accessible via fetch_dataset (e.g. Trex dataset)