Minor performance tweak

Author: rpavlik

adafruit_emc2101/emc2101_lut.py

@@ -93,7 +93,7 @@ def __repr__(self):
     def __str__(self):
         """return the official string representation of the LUT"""
         value_strs = []
-        lut_keys = list(sorted(self.lut_values.keys()))
+        lut_keys = tuple(sorted(self.lut_values.keys()))
         for temp in lut_keys:
             fan_drive = self.lut_values[temp]
             value_strs.append("%d deg C => %.1f%% duty cycle" % (temp, fan_drive))