input: Write a function to implement a basic version control system in Python that keeps track of changes in the code. The function should allow for committing changes and restoring to a previous version. If the log file is empty or there are no previous versions to restore, the function should return the original lines without changes.
  
  class VersionControl:
      def __init__(self, lines):
          self.lines = lines
          self.mark = 0
   
      def commit(self):
          self.mark += 1
          log_file = open("log_file.txt", "a+")
          log_file.write(str(self.mark) + ": " + str(self.lines))
          log_file.close()
   
      def restore(self):
          log_file = open("log_file.txt", "r")
          lines = log_file.readlines()
          to_mark = self.mark-1
   
          if to_mark >= 0 and to_mark < len(lines):
              self.lines = lines[to_mark].split(": ")[1]
          log_file.close()
  
  assert VersionControl(['line1', 'line2']).commit() == None
  assert VersionControl(['line1', 'line2']).restore() == None
  assert VersionControl([]).commit() == None
  assert VersionControl([]).restore() == None
  assert VersionControl(['line1', 'line2', 'line3']).commit() == None
  assert VersionControl(['line1', 'line2', 'line3']).restore() == None
output: 
  def __init__(self, lines):
      self.lines = lines
      self.mark = 0
  
  def commit(self):
      self.mark += 1
      with open("log_file.txt", "a+") as log_file:
          log_file.write(str(self.mark) + ": " + str(self.lines) + "\n")
  
  def restore(self):
      with open("log_file.txt", "r") as log_file:
          lines = log_file.readlines()
          to_mark = self.mark - 1
          if to_mark >= 0 and to_mark < len(lines):
              self.lines = eval(lines[to_mark].split(": ", 1)[1])
  