title: <AG-Grid> Property 'children' does not exist on type 'ColDef<object>'
body: <p>trying to do a project on AG grid but I am coming across an error with typescript. It says ([AG-Grid] Property 'children' does not exist on type 'ColDef') getting this error around the filter method below where (column =&gt; column.children).</p>
  <p>I went to the documentation of ag-grid but I can see that column defs support using children as a property. So I am not sure why I am getting this error?</p>
  <p><a href="https://i.stack.imgur.com/9GTmE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9GTmE.png" alt="enter image description here" /></a></p>
  <pre><code>import { ColDef, ColGroupDef } from 'ag-grid-community';
  
  export const sampleItems: Array&lt;{
    label: string;
    value: string;
  }&gt; = [];
  
  export const TABLE_COLUMN = [
    {
      headerName: 'User',
      children: [
        {
          field: 'user',
          headerName: 'Name',
          pinned: 'left',
          type: 'fixed',
        },
        { field: 'account', pinned: 'left', type: 'fixed' },
        {
          field: 'price',
          headerName: 'Pricing',
          pinned: 'left',
          type: 'primary',
        },
      ],
    },
    {
      headerName: 'Address',
      children: [
        { field: 'address', headerName: 'Address', type: 'secondary' },
        {
          field: 'street',
          headerName: 'Street Name',
          columnGroupShow: 'closed',
          type: 'secondary',
        },
      ],
    },
  ] as (ColDef&lt;object&gt; | ColGroupDef&lt;object&gt;)[];
  
  
  TABLE_COLUMN.filter((column) =&gt; column.children != null).forEach(
    (column) =&gt; {
      column.children.forEach((child) =&gt; {
        if (child.type === 'fixed' || child.type === 'primary') {
          sampleItems.push({
            label:
              child.headerName ??
              child.field.charAt(0).toUpperCase() + child.field.slice(1),
            value: child.field,
          });
        }
      });
    },
  );
  </code></pre>