docs: @Nonnull
      public static List<String> splitAtCommasAndTrim(Iterable<String> input) {
          if(input==null) {
              return Collections.emptyList();
          }
          Iterable<String> nonEmptyInputs = Iterables.filter(input, Predicates.notNull());
          return Lists.newArrayList(Iterables.concat(Iterables.transform(nonEmptyInputs, COMMA_SPLITTER)));
      }