Unmarshalling DynamoDB array;

I am trying to unmarshall the below array:

let arr = [{"m_id":"62","reporting_categories":[{"M":{"report_category_cd":{"S":"L"},"report_category":{"S":"Light Vehicles"}}},{"M":{"report_category_cd":{"S":"M"},"report_category":{"S":"Motorcycles"}}}]},
{"m_id":"61","reporting_categories":[{"M":{"report_category_cd":{"S":"L"},"report_category":{"S":"Extra Light Vehicles"}}},{"M":{"report_category_cd":{"S":"M"},"report_category":{"S":"Bikes"}}}]}] 

I tried: AWS.DynamoDB.Converter.unmarshall(arr); but it didn't work.

Expected output:

let arr = [{"m_id":"62","reporting_categories":[{
    report_category_cd: "L",
    report_category: "Light Vehicles"
},{
    report_category_cd: "M",
    report_category: "Motorcycles"
}]
},
{"m_id":"61","reporting_categories":[{
    report_category_cd: "L",
    report_category: "Extra Light Vehicles"
},{
    report_category_cd: "M",
    report_category: "Bikes"
}]
}];