new_contents: data_file = open('data.txt', 'r')
  data_file2 = data_file.read()
  data_file2 = data_file2.split("\n")
  data_file.close()
  
  num_lines = len([l for l in data_file2 if l.strip(' \n') != ''])
  
  i = 0
  subject = [] 
  tag = []
  group = []
  student = []
  
  while i < num_lines:
      if data_file2[i] == "<subject>":
          subject.append([data_file2[i+1],data_file2[i+2],data_file2[i+3]])
          i=i+1
      elif data_file2[i] == "<tag>":
          tag.append([data_file2[i+1],data_file2[i+2]])
          i=i+1
      elif data_file2[i] == "<group>":
          group.append([data_file2[i+1]])
          i=i+1
      elif data_file2[i] == "<student>":
          student.append([data_file2[i+1],data_file2[i+2]])
          i=i+1
      else:
          i=i+1
  print(subject)
  print("---------------------------------------------------")
  print(tag)
  print("---------------------------------------------------")
  print(group)
  print("---------------------------------------------------")
  print(student)
  print("---------------------------------------------------")  
  
subject: Create Model.py