code: def file_checksum(fname):
      
      size = os.path.getsize(fname)
      with open(fname, "r+") as f:
          checksum = hashlib.md5(mmap.mmap(f.fileno(), size)).hexdigest()
      return checksum
docs: Return md5 checksum of file.
  
      Note: only works for files < 4GB.
  
      Parameters
      ----------
      filename : str
          File used to calculate checksum.
  
      Returns
      -------
          checkum : str