[BUG]: AttributeError: 'list' object has no attribute 'shape' 
If I try the scripts/tsne.py, then bug occurs
```
$ python3 scripts/tsne.py --smiles_paths tests/data/classification.csv --save_path tests/data/classification.png
```
```
Loading data
classification: 500
Computing Morgan fingerprints
  0%|                                                                                                                                                                                                                 | 0/500 [00:00<?, ?it/s][15:12:09] WARNING: not removing hydrogen atom without neighbors
100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 500/500 [00:00<00:00, 4214.68it/s]
Running t-SNE
Traceback (most recent call last):
  File "/opt/chemprop/scripts/tsne.py", line 122, in <module>
    compare_datasets_tsne(Args().parse_args())
  File "/opt/chemprop/scripts/tsne.py", line 70, in compare_datasets_tsne
    X = tsne.fit_transform(morgans)
  File "/opt/conda/lib/python3.9/site-packages/sklearn/manifold/_t_sne.py", line 1118, in fit_transform
    self._check_params_vs_input(X)
  File "/opt/conda/lib/python3.9/site-packages/sklearn/manifold/_t_sne.py", line 828, in _check_params_vs_input
    if self.perplexity >= X.shape[0]:
AttributeError: 'list' object has no attribute 'shape'
```

diff --git a/scripts/tsne.py b/scripts/tsne.py
index f206af43..97bdaf6b 100644
--- a/scripts/tsne.py
+++ b/scripts/tsne.py
@@ -62,7 +62,7 @@ def compare_datasets_tsne(args: Args):
     # Compute Morgan fingerprints
     print('Computing Morgan fingerprints')
     morgan_generator = get_features_generator('morgan')
-    morgans = [morgan_generator(smile) for smile in tqdm(smiles, total=len(smiles))]
+    morgans = np.array([morgan_generator(smile) for smile in tqdm(smiles, total=len(smiles))])
 
     print('Running t-SNE')
     start = time.time()
['scripts/tsne.py']