docs: def _build_row(padded_cells, colwidths, colaligns, rowfmt):
      "Return a string which represents a row of data cells."
      if not rowfmt:
          return None
      if hasattr(rowfmt, "__call__"):
          return rowfmt(padded_cells, colwidths, colaligns)
      else:
          return _build_simple_row(padded_cells, rowfmt)