Try--except different cadnano versions syntax

mrdna/readers/cadnano_segments.py

@@ -199,7 +199,14 @@ class cadnano_part(SegmentModel):
                               dimensions=(5000,5000,5000))
 
     def _cadnano_part_to_segments(self,part):
-        from cadnano.cnenum import PointType
+        try:
+            from cadnano.cnenum import PointType
+        except:
+            try:
+                from cadnano.proxies.cnenum import PointType
+            except:
+                from cadnano.proxies.cnenum import PointEnum as PointType
+
         segments = dict()
         self.helices = helices = dict()
         self.helix_ranges = helix_ranges = dict()