Custom Entity field of type long_text not storing values I created a entity.

$fields['supplemental'] = BaseFieldDefinition::create('text_long')
                -&gt;setLabel(t('Supplemental'))
                -&gt;setDescription(t('Answer description.'))
                -&gt;setDisplayOptions('view', array(
                    'label' =&gt; 'hidden',
                    'type' =&gt; 'text_default',
                    'weight' =&gt; -3,
                ))
                -&gt;setDisplayOptions('form', array(
                    'type' =&gt; 'text_textfield',
                    'weight' =&gt; -3,
                ))
                //-&gt;setRequired(TRUE)
                -&gt;setDisplayConfigurable('form', TRUE)
                -&gt;setDisplayConfigurable('view', TRUE);


And I'm saving data into this entity's field like

$mcq = Mcq::create(array(
           'supplemental__value' =&gt; $value-&gt;supplemental,
            'supplemental__format'=&gt;'basic_html',
        )); 
$mcq-&gt;save();


Issue is all fields gets populated except of type 'text_long'. Am I missing something or there is any other way of populating entity field values.
After realising few minutes later, the column name should be supplemental not supplemental__value.

I was mapping content by looking into database columns which was wrong.