new_contents: """
  Utilities to work with LaTeX files.
  """
  
  import argparse
  import re
  
  def read_tex_file(tex_file, encoding="utf-8"):
      with open(tex_file, 'r', encoding=encoding) as data:
          tex_source = data.read()
      return tex_source
  
  
  def write_tex_file(tex_file, tex_source):
      with open(tex_file, 'w') as open_file:
          open_file.write(tex_source)
          
  
  def get_relevant_warnings(log_file):
      """Extract relevant warnings from a LaTeX log file."""
      overfull_lines = re.findall(r"Overfull \\hbox .*", log_file)
      undefined_references = re.findall(r"LaTeX Warning: Citation `.*?' on page .*", log_file)
      return overfull_lines + undefined_references
  
          
  def cli_parser():
      parser = argparse.ArgumentParser()
      parser.add_argument('tex_file')
      parser.add_argument("--debug", action="store_true")
      args = parser.parse_args()
      return args
  
  
  if __name__ == "__main__":
      args = cli_parser()
      log_file = read_tex_file(args.tex_file, encoding="latin-1")
      relevant_warnings = get_relevant_warnings(log_file)
      for warning in relevant_warnings:
          print(warning)
  
  
  
subject: Add utilities to work with LaTeX files