title: AWS Cloudformation Stringlist error
body: <p><strong>ERROR:</strong> Property validation failure: [Value of property {/StreamingDistributionConfig/TrustedSigners/AwsAccountNumbers} does not match type {Array}].</p>
  
  <p>I am trying to get multiple account Id's in a parameter called awsAccountNumbers, for which the cloudformation document says this parameter must be of type StringList. However, there's no such type. We have <strong>String</strong> and <strong>CommaDelimitedList</strong> in the AWS parameters reference for which I get the mentioned error. I tried splitting it too, but of no help. Please find my code below: </p>
  
  <pre><code>**Parameters Section:** 
    "awsAccountNumbers": {
              "Type": "String",
  
    }
  
  **Resources Section:** 
  
     "TrustedSigners": {
                          "AwsAccountNumbers": {
                              "Fn::If": [
                                  "withRestrictViewerAccessasYes",
                                  {
                                      "Fn::If": [
                                          "withTrustedSignersasSelf",
                                          "882410330966",
                                          [
                                              {
                                                  "Fn::Select": [
                                                      "0",
                                                      {
                                                          "Fn::Split": [
                                                              ",",
  
                                                              { "Ref": "awsAccountNumbers" }
  
                                                          ]
                                                      }
                                                  ]
                                              }
                                          ]
                                      ]
                                  },
                                  {
                                      "Ref": "AWS::NoValue"
                                  }
                              ]
                          },
                          "Enabled": {
                              "Ref": "trustedSignersEnabled"
                          }
                      }
  </code></pre>