make get_polygon_bounds clearer

Signed-off-by: Julien Veyssier <eneiluj@posteo.net>

modules/hrudelin_1_init.py

@@ -73,12 +73,12 @@ def get_polygon_bounds(shape, xmin_slect, ymax_slect, xmax_slect, ymin_slect):
     ds = ogr.Open(shape)
     layer = ds.GetLayer()
     xmin, xmax, ymin, ymax = layer.GetExtent()
-    xmin_slect = max(xmin_slect, xmin)
-    xmax_slect = min(xmax_slect, xmax)
-    ymin_slect = max(ymin_slect, ymin)
-    ymax_slect = min(ymax_slect, ymax)
-
-    return xmin_slect, ymax_slect, xmax_slect, ymin_slect
+    return (
+        max(xmin_slect, xmin),
+        min(ymax_slect, ymax),
+        min(xmax_slect, xmax),
+        max(ymin_slect, ymin)
+    )
 
 def get_coords(parms, xmin_slect, ymax_slect, xmax_slect, ymin_slect):
     xmin_slect = max(xmin_slect, float(parms.get('surface', 'west')))