class_docstr: Reads in the a Triplet Dataset: Each line contains (at least) 3 columns, one anchor column (s1),
  one positive example (s2) and one negative example (s3)
code: def __init__(
      self,
      dataset_folder,
      s1_col_idx=0,
      s2_col_idx=1,
      s3_col_idx=2,
      has_header=False,
      delimiter="\t",
      quoting=csv.QUOTE_NONE,
  ):
      self.dataset_folder = dataset_folder
      self.s1_col_idx = s1_col_idx
      self.s2_col_idx = s2_col_idx
      self.s3_col_idx = s3_col_idx
      self.has_header = has_header
      self.delimiter = delimiter
      self.quoting = quoting
  
imports: from .None import InputExample
  import csv
  import os
label_desc: Use image node_id 1 to create a new TripletReader object from inherited base classes: object with example: obj = TripletReader(dataset_folder, s1_col_idx, s2_col_idx, s3_col_idx, has_header, delimiter, quoting)