title: Boto 3 DynamoDB batchWriteItem Invalid attribute value type when specifying types
body: <p>I have a strange problem with Python Boto3 when trying to do a batch_write_item to a DynamoDB table. I am following the <a href="http://boto3.readthedocs.io/en/latest/reference/services/dynamodb.html#DynamoDB.Client.batch_write_item" rel="noreferrer">documentation</a> and trying to write a singe item. The table is setup correctly and I can run batch-write-item via the AWS cli no problem.</p>
  
  <p>Assuming the client and DynamoDB are set up correctly I run:</p>
  
  <pre><code>client.batch_write_item(RequestItems={
      "myTable": [
          {
              "PutRequest": {
                  "Item": {
                      "name": {
                          "S": "hello"
                      },
                      "value": {
                          "S": "world"
                      }
                  }
              }
          }
      ]
  })
  </code></pre>
  
  <p>I get the following error:</p>
  
  <p><strong>botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the BatchWriteItem operation: Invalid attribute value type</strong></p>
  
  <p>If I change it, removing the types and run:</p>
  
  <pre><code>client.batch_write_item(RequestItems={
      "myTable": [
          {
              "PutRequest": {
                  "Item": {
                      "name": "hello",
                      "value": "world"
                  }
              }
          }
      ]
  })
  </code></pre>
  
  <p>It works as expected.</p>
  
  <p>I need to use the previous format which follows the documentation and is compatibale with AWS cli.</p>
  
  <p>Is the documentation wrong or I missed a configuration setting, version issue or something else?</p>