class_docstr: Simple Tensorizer that splits a sentence on spaces and create tensors
  from the vocabulary index built on the training data.
code: def sort_key(self, row):
      # LSTM representations need the batches to be sorted by descending seq_len
      return row[1]
  
file_path: pytext/demo/examples/tensorizer.py
imports: from pytext.data.tensorizers import Tensorizer
  from pytext.data.utils import pad_and_tensorize, VocabBuilder
label_desc: Use image node_id 8 for calling the MyWordTensorizer obj's underlying member method code with example usage: obj.sort_key(row) and returns: row