ultralytics 8.1.43 40% faster ultralytics imports (#9547)

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/utils/metrics.py

@@ -395,19 +395,19 @@ class ConfusionMatrix:
             names (tuple): Names of classes, used as labels on the plot.
             on_plot (func): An optional callback to pass plots path and data when they are rendered.
         """
-        import seaborn as sn
+        import seaborn  # scope for faster 'import ultralytics'
 
         array = self.matrix / ((self.matrix.sum(0).reshape(1, -1) + 1e-9) if normalize else 1)  # normalize columns
         array[array < 0.005] = np.nan  # don't annotate (would appear as 0.00)
 
         fig, ax = plt.subplots(1, 1, figsize=(12, 9), tight_layout=True)
         nc, nn = self.nc, len(names)  # number of classes, names
-        sn.set_theme(font_scale=1.0 if nc < 50 else 0.8)  # for label size
+        seaborn.set_theme(font_scale=1.0 if nc < 50 else 0.8)  # for label size
         labels = (0 < nn < 99) and (nn == nc)  # apply names to ticklabels
         ticklabels = (list(names) + ["background"]) if labels else "auto"
         with warnings.catch_warnings():
             warnings.simplefilter("ignore")  # suppress empty matrix RuntimeWarning: All-NaN slice encountered
-            sn.heatmap(
+            seaborn.heatmap(
                 array,
                 ax=ax,
                 annot=nc < 30,