Using JSON Standard Import API, how to specify "text" for Container shape

Hi, 
I’m new to LucidCharts and am trying to use the JSON standard import API to create a diagram. 
I am able to upload the json file to see the rendered diagram and that’s all good. However, for a container shape that I want to use, I am unable to specify text that appears in the shape. 

Below is a simple JSON file that makes use of containers. I’ve specified 2 different ways to create the container, and for both, I can’t see text in the diagram. 

Can someone point out how to specify text for the container shapes with id=”containerTest” and “container1”? (I would prefer to use “container1” formatting). 

After making manual changes to the rendered diagram, I would like to export this diagram to CSV, having the shape text appear in the “Text Area 1” or “Text Area 2” columns. 
 

{
    "product": "lucidchart",
    "version": 1,
    "pages": [
        {
            "id": "Page1",
            "title": "TestingBlocks",
            "settings": {
                "size": {
                "type": "letter",
                "format": "landscape"
                }
            },
            "shapes": [
            {
                "id": "containerTest",
                "type": "rectangle",
                "style": {
                   "fill": {
                       "type": "color",
                       "color": "#F0F0F0"
                   },
                   "stroke":{
                       "color": "#000000",
                       "width": 1,
                       "style": "solid"
                   }
                },
                "boundingBox": {
                    "x": 100,
                    "y": 700,
                    "w": 200,
                    "h": 200
                },
                "isContainer":true,
                "shapes": [
                    {
                        "id": "text1",
                        "type": "Text",
                        "boundingBox": {
                            "x": 110,
                            "y": 710,
                            "w": 180,
                            "h": 20
                        },
                        "text": "CONTAINER C",
                        "style": {
                            "font": {
                                "family": "Arial",
                                "size": 8,
                                "bold": false
                            },
                            "alignment": "center"
                        }
                    }
                ],
                "opacity": 50,
                "zIndex": 0
            },
            {
                "id": "container1",
                "type": "roundedRectangleContainer",
                "text": "containerAB",
                "boundingBox": {
                    "x": 200,
                    "y": 50,
                    "h": 500
                    "w": 700,
                },
                "magnetize": true
            },
            {
                "id": "block_1",
                "type": "rectangle",
                "customData": [
                    {
                        "key": "Num",
                        "value": "1"
                    }
                ],
                "boundingBox": {
                    "x": 300,
                    "y": 100,
                    "w": 200,
                    "h": 200
                },
                "text": "A\n block {{=@Num}}"
            },
            {
                "id": "block_3",
                "type": "rectangle",
                "customData": [
                    {
                        "key": "Num",
                        "value": "3"
                    }
                ],
                "boundingBox": {
                    "x": 600,
                    "y": 100,
                    "w": 200,
                    "h": 200
                },
                "text": "B\n block {{=@Num}}"
            }
            ],
            "lines": []
        }
    ]
}