Missing Attributes

When I drag a block into the canvas, some attributes of that block is missing

blocks: [
                  {
                    label: 'Container',
                    content: '<div data-gjs-test="true" class="container"></div>',

                  },//end of container
]

from the above example the "data-gjs-test" was removed after dragging the block into the canvas. I want it to remain . Thank you