documentation update

data-processing-lib/doc/transform-exceptions.md

@@ -8,8 +8,12 @@ With this in mind, there are two types of exceptions:
 1. Those that would not allow any data to be processed (e.g. model loading problem).
 2. Those that would not allow a specific datum to be processed (e.g. missing column).
 
-In the first situation the transform should throw an exception from the initializer, which
+In the first situation the transform should throw an 
+[unrecoverable exception](../python/src/data_processing/utils/unrecoverable.py), which
 will cause the runtime to terminate processing of all data. 
+**Note:** any exception thrown from `init` method of transform will cause runtime to 
+terminate processing
+
 In the second situation (identified in the `transform()` or `flush()` methods), the transform
 should throw an exception from the associated method.
 This will cause only the error-causing datum to be ignored and not written out,