input: 
  from typing import List
  
  
  class VersionControl:
      def __init__(self, lines: List[str]):
          self.lines = lines
          self.mark = 0
  
      def commit(self) -> None:
          """
          Commits the current state of the lines to a log file and increments the mark.
          >>> vc = VersionControl(['line1', 'line2'])
          >>> vc.commit()
          >>> vc.mark
          1
          """
          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) -> None:
          """
          Restores the lines to the state of the previous mark.
          >>> vc = VersionControl(['line1', 'line2'])
          >>> vc.commit()
          >>> vc.lines.append('line3')
          >>> vc.commit()
          >>> vc.restore()
          >>> vc.lines
          ['line1', 'line2']
          """
          log_file = open("log_file.txt", "r")
          lines = log_file.readlines()
          to_mark = self.mark - 1
          self.lines = eval(lines[to_mark].split(": ")[1])
          log_file.close()
  
output:     
          self.mark = to_mark
  