code: def data2vw(ifn, train, test, names):
      lineno = 0
      trainN = 0
      testN = 0
      if ifn.endswith(".gz"):
          import gzip
  
          iopener = gzip.open
      else:
          iopener = open
      id_pos = names.index("id")
      letter_pos = names.index("letter")
      pixel_start = find_pixel_start(names)
      with iopener(ifn) as ins, open(train, "wb") as trainS, open(
          test, "wb"
      ) as testS:
          for line in ins:
              lineno += 1
              vals = line.rstrip().split("\t")
              if len(vals) != len(names):
                  raise ValueError(
                      "Bad field count",
                      len(vals),
                      len(names),
                      vals,
                      names,
                  )
              char = vals[letter_pos]
              if len(char) != 1:
                  raise ValueError("Bad letter", char)
              if lineno % 10 == 0:
                  testN += 1
                  outs = testS
              else:
                  trainN += 1
                  outs = trainS
              outs.write(
                  "%d 1 %s-%s|Pixel"
                  % (ord(char) - ord("a") + 1, char, vals[id_pos])
              )
              for i in range(pixel_start, len(names)):
                  if vals[i] != "0":
                      outs.write(" %s:%s" % (names[i], vals[i]))
              outs.write("\n")
      print(
          "Read %d lines from %s; wrote %d lines into %s and %d lines into %s"
          % (lineno, ifn, trainN, train, testN, test)
      )
  
label_desc: Use image node_id 3 for calling a global function with example usage: data2vw(ifn, train, test, names) without return types