Remove reference_video_tensor() fixture (#62)

Summary:
This PR removes `reference_video_tensor()` because its unnecessary.

I assume the use of this fixture was used to cache the corresponding returned value. This is unnecessary for 2 reasons:

- The fixture wasn't even cached anyway, because its scope wasn't set to `"session"`. You can verify that by printing something within the fixture, and running tests with `pytest -s`. You'll see the print statement being executed each time, proving that no caching was involved.
- Getting the return value is dead cheap and doesn't need to be cached in the first place. Proof:

```py
[ins] In [1]: import test_utils
tes
[nav] In [2]: %timeit test_utils.NASA_VIDEO.to_tensor()
55.8 µs ± 3.76 µs per loop (mean ± std. dev. of 7 runs, 10,000 loops each)
```

Pull Request resolved: #62

Reviewed By: scotts

Differential Revision: D59449321

Pulled By: NicolasHug

fbshipit-source-id: a848654115054e1526204d697d1d14748808ef91

test/samplers/video_clip_sampler_test.py

@@ -10,10 +10,7 @@
     VideoClipSampler,
 )
 
-from ..test_utils import (  # noqa: F401; see use in test_sampler
-    assert_tensor_equal,
-    reference_video_tensor,
-)
+from ..test_utils import assert_tensor_equal, NASA_VIDEO
 
 
 @pytest.mark.parametrize(
@@ -33,15 +30,12 @@
         ),
     ],
 )
-def test_sampler(
-    sampler_args,
-    reference_video_tensor,  # noqa: F811; linter does not see this as a use
-):
+def test_sampler(sampler_args):
     torch.manual_seed(0)
     desired_width, desired_height = 320, 240
     video_args = VideoArgs(desired_width=desired_width, desired_height=desired_height)
     sampler = VideoClipSampler(video_args, sampler_args)
-    clips = sampler(reference_video_tensor)
+    clips = sampler(NASA_VIDEO.to_tensor())
     assert_tensor_equal(len(clips), sampler_args.clips_per_video)
     clip = clips[0]
     if isinstance(sampler_args, TimeBasedSamplerArgs):

test/test_utils.py

@@ -5,7 +5,6 @@
 from dataclasses import dataclass
 
 import numpy as np
-import pytest
 
 import torch
 
@@ -36,11 +35,6 @@ def _load_tensor_from_file(filename: str) -> torch.Tensor:
     return torch.load(file_path, weights_only=True)
 
 
-@pytest.fixture()
-def reference_video_tensor() -> torch.Tensor:
-    return NASA_VIDEO.to_tensor()
-
-
 @dataclass
 class TestContainerFile:
     filename: str