code: def _build_hline(self, is_header=False):
          
          horiz = self._char_horiz
          if (is_header):
              horiz = self._char_header
          # compute cell separator
          s = "%s%s%s" % (horiz, [horiz, self._char_corner][self._has_vlines()],
              horiz)
          # build the line
          l = s.join([horiz * n for n in self._width])
          # add border if needed
          if self._has_border():
              l = "%s%s%s%s%s\n" % (self._char_corner, horiz, l, horiz,
                  self._char_corner)
          else:
              l += "\n"
          return l
docs: Return a string used to separated rows or separate header from
          rows