Merchant Fulfillment - CreateShipment

[shantikolli]

Can someone tell how does the file contents of the label look like.
The sandbox response from Amazon documentation :
{
"payload": {
"ShipmentId": "be7a0a53-00c3-4f6f-a63a-639f76ee9253",
"AmazonOrderId": "903-5563053-5647845",
"Insurance": {
"CurrencyCode": "USD",
"Amount": 0
},
"ItemList": [
{
"OrderItemId": "12958298061782",
"Quantity": 1
}
],
"ShipFromAddress": {
"Name": "John Doe",
"AddressLine1": "300 Turnbull Ave",
"Email": "[email protected]",
"City": "Detroit",
"StateOrProvinceCode": "MI",
"PostalCode": "48123",
"CountryCode": "US",
"Phone": "7132341234"
},
"ShipToAddress": {
"Name": "New York",
"AddressLine1": "TIME WARNER CENTER",
"AddressLine2": "10 COLUMBUS CIR",
"Email": "",
"City": "NEW YORK",
"StateOrProvinceCode": "NY",
"PostalCode": "10019-1158",
"CountryCode": "US",
"Phone": ""
},
"PackageDimensions": {
"Length": 10.25,
"Width": 10.25,
"Height": 10.25,
"Unit": "inches"
},
"Weight": {
"Value": 10.25,
"Unit": "oz"
},
"ShippingService": {
"ShippingServiceName": "UPS 2nd Day Air®",
"CarrierName": "UPS®",
"ShippingServiceId": "UPS_PTP_2ND_DAY_AIR",
"ShippingServiceOfferId": "WHgxtyn6qjGGaCzOCog1azF5HLHje5Pz3Lc2Fmt5eKoZAReW8oJ1SMumuBS8lA/Hjuglhyiu0+KRLvyJxFV0PB9YFMDhygs3VyTL0WGYkGxiuRkmuEvpqldUn9rrkWVodqnR4vx2VtXvtER/Ju6RqYoddJZGy6RS2KLzzhQ2NclN0NYXMZVqpOe5RsRBddXaGuJr7oza3M52+JzChocAHzcurIhCRynpbxfmNLzZMQEbgnpGLzuaoSMzfxg90/NaXFR/Ou01du/uKd5AbfMW/AxAKP9ht6Oi9lDHq6WkGqvjkVLW0/jj/fBgblIwcs+t",
"ShipDate": "2019-10-28T16:37:37Z",
"EarliestEstimatedDeliveryDate": "2019-10-30T07:00:00Z",
"LatestEstimatedDeliveryDate": "2019-10-30T07:00:00Z",
"Rate": {
"CurrencyCode": "USD",
"Amount": 34.73
},
"ShippingServiceOptions": {
"DeliveryExperience": "NoTracking",
"DeclaredValue": {
"CurrencyCode": "USD",
"Amount": 0
}
},
"RequiresAdditionalSellerInputs": false
},
"Label": {
"Dimensions": {
"Length": 6.0,
"Width": 4.0,
"Unit": "inches"
},
"FileContents": {
"Contents": "H4sIAAAAAAAAAOR",
"FileType": "image/png",
"Checksum": "d+eUxK5WTGxkGsTF0pmefQ=="
},
"LabelFormat": "PNG"
},
"Status": "Purchased",
"TrackingId": "1Z17E2100217295733",
"CreatedDate": "2019-10-28T16:37:43Z"
}
}

Why is the contents like this? how is it supposed to be converted?
"Contents": "H4sIAAAAAAAAAOR",