<table class="st-331a3ced">
    <style>
        .st-331a3ced {
            border: none;
            margin: 0 auto;
            padding: 0.25rem;
            border-collapse: separate;
            border-spacing: 0.85em 0.2em;
            line-height: 1.2em;
        }

        .st-331a3ced tr td {
            vertical-align: top;
            padding: 0;
            border: none;
        }

        .st-331a3ced br {
            line-height: 0em;
            margin: 0;
        }

        .st-331a3ced sub {
            line-height: 0;
        }

        .st-331a3ced sup {
            line-height: 0;
        }
    </style>
    <tr><td colspan="3" style="border-bottom: 1.5px solid currentColor; padding: 0"></td></tr>
    <tr>
        <td style="text-align:center;"></td>
        <td colspan="2" style="font-weight:bold;border-bottom:1px solid currentColor; padding-bottom: 0.25em;text-align:center;">group1</td>
    </tr>
    <tr>
        <td style="text-align:center;"></td>
        <td colspan="2" style="text-align:center;">a</td>
    </tr>
    <tr>
        <td style="text-align:center;"></td>
        <td colspan="2" style="font-weight:bold;border-bottom:1px solid currentColor; padding-bottom: 0.25em;text-align:center;">group2</td>
    </tr>
    <tr>
        <td style="text-align:center;"></td>
        <td style="text-align:center;">e</td>
        <td style="text-align:center;">f</td>
    </tr>
    <tr>
        <td style="font-weight:bold;text-align:left;">group3</td>
        <td colspan="2" style="font-weight:bold;text-align:center;">value1</td>
    </tr>
        <tr><td colspan="3" style="border-bottom:1px solid currentColor;padding:0"></td></tr>    <tr>
        <td style="text-align:left;">c</td>
        <td style="text-align:center;">1</td>
        <td style="text-align:center;">2</td>
    </tr>
    <tr>
        <td style="text-align:left;">d</td>
        <td style="text-align:center;">3</td>
        <td style="text-align:center;">4</td>
    </tr>
    <tr><td colspan="3" style="border-bottom: 1.5px solid currentColor; padding: 0"></td></tr>
</table>