Fix missing sampler argument in xaeronet volume dataloader demo

[Anai-Guo]

Problem

examples/cfd/external_aerodynamics/xaeronet/volume/dataloader.py cannot be run as a
script. create_dataloader takes sampler as a required positional argument:

def create_dataloader(
    file_list, mean, std, sampler, nan_to_0=True, batch_size=1, ...
):

but the __main__ demo block at the bottom of the same file omits it:

dataloader = create_dataloader(
    file_list, mean, std, nan_to_0=True, batch_size=2, num_workers=1
)

so python dataloader.py fails with
TypeError: create_dataloader() missing 1 required positional argument: 'sampler'
before any data is touched.

Two things show sampler was added to the signature after this demo was written and
the demo was never updated:

• The docstring documents file_list, mean, std, batch_size, num_workers,
  pin_memory and prefetch_factor — but neither sampler nor nan_to_0.
• The sibling surface/dataloader.py has the same __main__ demo and runs fine,
  because its create_dataloader has no required sampler.

Fix

Pass sampler=None, exactly as the real training code in the same example already
does at volume/train.py:

valid_dataloader = create_dataloader(
    valid_dataset, mean, std, batch_size=1, num_workers=1, sampler=None
)

DataLoader(sampler=None) is the documented default (sequential order), so the demo
behaves as originally intended. Also documented sampler and nan_to_0 in the
docstring.

Verification

No GPU or DriveAer dataset here, so I verified the argument binding rather than
executing the loader — which is exactly where the failure is. Signatures were
extracted from the file's AST and each call shape replayed with Signature.bind:

create_dataloader (file_list, mean, std, sampler, nan_to_0=True, batch_size=1,
                   num_workers=4, pin_memory=True, prefetch_factor=2)
  volume/train.py:118 (real production call)     -> binds OK
  volume/dataloader.py __main__ (as written)     -> TypeError: missing a required argument: 'sampler'
  volume/dataloader.py __main__ (patched)        -> binds OK

Formatting, with the version pinned in .pre-commit-config.yaml (ruff v0.12.5), run
from the repo root:

$ ruff format --check examples/cfd/external_aerodynamics/xaeronet/volume/dataloader.py
1 file already formatted

(ruff check excludes ^examples/ in the pre-commit config; I confirmed the file's
ruff check output is byte-identical before and after this patch either way.)

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[github-actions]

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⏳ @mnabian — 1 file(s)

• examples/cfd/external_aerodynamics/xaeronet/volume/dataloader.py

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[greptile-apps]

Greptile Summary

The PR fixes the XAeroNet volume dataloader demo by explicitly passing sampler=None, allowing the call to satisfy the required function signature. It also documents the sampler and nan_to_0 parameters.

Important Files Changed

Filename	Overview
examples/cfd/external_aerodynamics/xaeronet/volume/dataloader.py	Correctly supplies the omitted required sampler argument in the demo and accurately documents both previously undocumented parameters.

_{Reviews (1): Last reviewed commit: "Fix missing `sampler` argument in xaeron..." | Re-trigger Greptile}