The description of keys of json data in data file, as follows:
{
     "title": "The title of the essay, which had been split to word", 
     "sents": "All sentences of the essay, which had been split to word",
     "labels": "The labels of every sentences", 
     "gid": "The Global position of every sentences", 
     "lid": "The Local position of every sentences", 
     "pid": "The Paragraph position of every sentences", 
}