speed up np_coerce

Author: victor-shepardson

src/anguilla/interpolate.py

@@ -122,7 +122,7 @@ def __call__(self, targets:List[Output], scores:List[float], eps:float=1e-6):
             return Nearest()(targets, scores)
 
         targets, scores = np_coerce(targets, scores)
-
+        
         scores = scores**0.5
 
         scores = scores + eps

src/anguilla/types.py

@@ -28,8 +28,9 @@ class SearchResult(NamedTuple):
     scores:Scores
 
 def _np_coerce(x):
-    if x is None:
-        return None
+    if x is None or isinstance(x, np.ndarray):
+        # no conversion
+        return x
     if hasattr(x, 'numpy'):
         # torch tensor, etc
         return x.numpy()