[sonic_platform_base] fix an indentation in fan_drawer_base.py (sonic…

…-net#133)

Fix the new definition of get_fan in fan_drawer_base.py

Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>

sonic_platform_base/fan_drawer_base.py

@@ -37,7 +37,7 @@ def get_all_fans(self):
         """
         return self._fan_list
 
-     def get_fan(self, index):
+    def get_fan(self, index):
         """
         Retrieves fan module represented by (0-based) index <index>