docs: def _iter_unfolded_lines(self):
          """Iter input unfoled lines. Skip comments."""
          line = self._input_file.readline()
          while line:
              self.line_counter += 1
              self.byte_counter += len(line)
  
              line = self._strip_line_sep(line)
  
              nextline = self._input_file.readline()
              while nextline and nextline[:1] == b' ':
                  line += self._strip_line_sep(nextline)[1:]
                  nextline = self._input_file.readline()
  
              if not line.startswith(b'#'):
                  yield line
              line = nextline