code: public List<Writable> executeSequenceToSingle(List<List<Writable>> inputSequence){
          return execute(null, inputSequence).getLeft();
      }
docs: Execute a TransformProcess that starts with a sequence
  record, and converts it to a single (non-sequence) record
  
  @param inputSequence Input sequence
  @return Record after processing (or null if filtered out)