title: Insert a Map in DynamoDB
body: <p>I'm trying to insert map data into a DynamoDB table using API Gateway. Here's my payload:</p>
  
  <pre><code>{
  "TableName":"OrderDB",
  "Item":{
      "_id": {"S":"04FA887FP2S5R"},
      "_rev": {"S":"9-12e098e2490e1b7c9782597226689403"},
      "_merchantId":{"S":"AXN3EKXT0SJ61"},
      "doc":{"M":{"something":"storedHere"} }
  }
  </code></pre>
  
  <p>And my body mapping template in API Gateway:</p>
  
  <pre><code>{ 
    "TableName": "$input.path('$.TableName')",
    "Item": $input.json('$.Item')
  }
  </code></pre>
  
  <p>Everything works as expected if I remove the <strong>doc</strong> item from the payload. With trying to post with the map I get the following error:</p>
  
  <pre><code>{
    "__type": "com.amazon.coral.service#SerializationException",
    "Message": "Unexpected value type in payload"
  }
  </code></pre>
  
  <p>All of the examples that I see suggest using the DynamoDB document mapping object, but I don't think this is possible for me because I'm using API Gateway to connect directly to DynamoDB. Is it possible to insert a map this way?</p>