input: Write a function to implement a basic version control system in Python that keeps track of changes in the code using a class `VersionControl`. The class should have an initializer that takes a list of lines and an integer mark set to 0. It should also have two methods: `commit` which increments the mark and writes the current state of lines to a log file, and `restore` which reads the log file and restores the lines to the state recorded at the previous mark.
  
  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
   
          self.lines = lines[to_mark]
          log_file.close()
  
  assert VersionControl(["print('Hello')", "print('World')"]).commit()==None
  assert VersionControl(["print('Goodbye')", "print('World')"]).commit()==None
  assert VersionControl([]).restore()==None
output: 
  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) + "\n")
          log_file.close()
   
      def restore(self):
          log_file = open("log_file.txt", "r")
          lines = log_file.readlines()
          log_file.close()
          to_mark = self.mark-1
          if to_mark >= 0 and to_mark < len(lines):
              self.lines = eval(lines[to_mark].split(": ", 1)[1])
  