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.
          
          >>> vc = VersionControl(["line1", "line2"])
          >>> vc.commit()
          >>> vc.mark
          1
          """
          self.mark += 1
          with open("log_file.txt", "a+") as log_file:
              log_file.write(f"{self.mark}: {self.lines}\n")
   
      def restore(self) -> None:
          """
          Restores the lines to the state saved in the previous commit.
          
          >>> vc = VersionControl(["line1", "line2"])
          >>> vc.commit()
          >>> vc.lines.append("line3")
          >>> vc.commit()
          >>> vc.restore()
          >>> vc.lines
          ['line1', 'line2']
          """
          with open("log_file.txt", "r") as log_file:
              lines = log_file.readlines()
              to_mark = self.mark - 1
              self.lines = eval(lines[to_mark].split(":")[1].strip())
  
output:     
          self.mark -= 1
  