how to exclude a field in datatable csv export

1dom: 'lBfrtip',
2buttons: [
3    {
4        extend: 'excelHtml5',
5        text: '<i class="fa fa-file-excel-o"></i> Excel',
6        titleAttr: 'Export to Excel',
7        title: 'Insurance Companies',
8        exportOptions: {
9            columns: ':not(:last-child)',
10        }
11    },
12    {
13        extend: 'csvHtml5',
14        text: '<i class="fa fa-file-text-o"></i> CSV',
15        titleAttr: 'CSV',
16        title: 'Insurance Companies',
17        exportOptions: {
18            columns: ':not(:last-child)',
19        }
20    },
21    {
22        extend: 'pdfHtml5',
23        text: '<i class="fa fa-file-pdf-o"></i> PDF',
24        titleAttr: 'PDF',
25        title: 'Insurance Companies',
26        exportOptions: {
27            columns: ':not(:last-child)',
28        },
29    },
30]