nn_descent import issues (#499)

* import early

* release note

Author: Intron7

docs/release-notes/0.13.5.md

@@ -0,0 +1,16 @@
+### 0.13.5 {small}`the-future`
+
+```{rubric} Features
+```
+
+```{rubric} Performance
+```
+* Improves `pp.neighbors` performance with `all_neighbors` and `nn_descent` when a Dask cluster is active {pr}`499` {smaller}`S Dicks`
+
+
+```{rubric} Bug fixes
+```
+
+
+```{rubric} Misc
+```

docs/release-notes/index.md

@@ -3,6 +3,8 @@
 # Release notes
 
 ## Version 0.13.0
+```{include} /release-notes/0.13.5.md
+```
 ```{include} /release-notes/0.13.4.md
 ```
 ```{include} /release-notes/0.13.3.md

src/rapids_singlecell/preprocessing/_neighbors/_algorithms/_all_neighbors.py

@@ -7,6 +7,10 @@
 
 from rapids_singlecell.preprocessing._neighbors._helper import _compute_nlist
 
+try:
+    from cuvs.neighbors import all_neighbors
+except ImportError:
+    all_neighbors = None
 if TYPE_CHECKING:
     from collections.abc import Mapping
 
@@ -22,9 +26,7 @@ def _all_neighbors_knn(
     metric_kwds: Mapping,
     algorithm_kwds: Mapping,
 ) -> tuple[cp.ndarray, cp.ndarray]:
-    try:
-        from cuvs.neighbors import all_neighbors
-    except ImportError:
+    if all_neighbors is None:
         raise ImportError(
             "The 'all_neighbors' algorithm is only available in cuvs >= 25.10. "
             "Please update your cuvs installation."

src/rapids_singlecell/preprocessing/_neighbors/_algorithms/_nn_descent.py

@@ -3,14 +3,19 @@
 from typing import TYPE_CHECKING
 
 import cupy as cp
-from packaging.version import parse as parse_version
 
 if TYPE_CHECKING:
     from collections.abc import Mapping
 
     from rapids_singlecell.preprocessing._neighbors import _Metrics
 
 
+try:
+    from cuvs.neighbors import nn_descent
+except ImportError:
+    nn_descent = None
+
+
 def _nn_descent_knn(
     X: cp.ndarray,
     Y: cp.ndarray,
@@ -20,14 +25,11 @@ def _nn_descent_knn(
     metric_kwds: Mapping,
     algorithm_kwds: Mapping,
 ) -> tuple[cp.ndarray, cp.ndarray]:
-    from cuvs import __version__ as cuvs_version
-
-    if parse_version(cuvs_version) <= parse_version("24.12"):
-        raise ValueError(
+    if nn_descent is None:
+        raise ImportError(
             "The 'nn_descent' algorithm is only available in cuvs >= 25.02. "
             "Please update your cuvs installation."
         )
-    from cuvs.neighbors import nn_descent
 
     # Extract intermediate_graph_degree from algorithm_kwds, with default
     intermediate_graph_degree = algorithm_kwds.get("intermediate_graph_degree", None)