code: def check_installed_files(self):
          
          mismatches = []
          record_path = os.path.join(self.path, 'installed-files.txt')
          if os.path.exists(record_path):
              for path, _, _ in self.list_installed_files():
                  if path == record_path:
                      continue
                  if not os.path.exists(path):
                      mismatches.append((path, 'exists', True, False))
          return mismatches
docs: Checks that the hashes and sizes of the files in ``RECORD`` are
          matched by the files themselves. Returns a (possibly empty) list of
          mismatches. Each entry in the mismatch list will be a tuple consisting
          of the path, 'exists', 'size' or 'hash' according to what didn't match
          (existence is checked first, then size, then hash), the expected
          value and the actual value.