tyler has defined a ``_repr_html_``
    to automatically render itself. Otherwise call Styler.to_html to get
    the generated HTML.

    CSS classes are attached to the generated HTML

    * Index and Column names include ``index_name`` and ``level<k>``
      where `k` is its level in a MultiIndex
    * Index label cells include

      * ``row_heading``
      * ``row<n>`` where `n` is the numeric position of the row
      * ``level<k>`` where `k` is the level in a MultiIndex

    * Column label cells include
      * ``col_heading``
      * ``col<n>`` where `n` is the numeric position of the column
      * ``level<k>`` where `k` is the level in a MultiIndex

    * Blank cells include ``blank``
    * Data cells include ``data``
    * Trimmed cells include ``col_trim`` or ``row_trim``.

    Any, or all, or these classes can be renamed by using the ``css_class_names``
    argument in ``Styler.set_table_classes``, giving a value such as
    *{"row": "MY_ROW_CLASS", "col_trim": "", "row_trim": ""}*.
    NT