input: 
  def VersionControl(lines):
      """ Implement a basic version control system in Python that keeps track of changes in the code.
      This system will have two main functions: commit and restore. The commit function will save the 
      current state of the code and increment the version mark. The restore function will revert the 
      code to the previous version mark. The changes are logged in a file named "log_file.txt".
      
      Example:
      vc = VersionControl(["print('hello world')", "x = 10"])
      vc.commit()
      vc.lines = ["print('goodbye world')", "x = 20"]
      vc.commit()
      vc.restore()
      print(vc.lines)  # Output: ["print('hello world')", "x = 10"]
      """
      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()
              to_mark = self.mark-1
              if to_mark >= 0:
                  self.lines = eval(lines[to_mark].split(": ", 1)[1])
              log_file.close()
  
output:     def __init__(self, lines):
              self.lines = lines
              self.mark = 0
              self.log_file = "log_file.txt"
              with open(self.log_file, "w") as f:
                  f.write(f"0: {self.lines}\n")
  
          def commit(self):
              self.mark += 1
              with open(self.log_file, "a") as f:
                  f.write(f"{self.mark}: {self.lines}\n")
  
          def restore(self):
              with open(self.log_file, "r") as f:
                  lines = f.readlines()
              to_mark = self.mark - 1
              if to_mark >= 0:
                  self.lines = eval(lines[to_mark].split(": ", 1)[1])
                  self.mark = to_mark