Error: Error Updating IAM Role (lambda_exec) Assume Role Policy: MalformedPolicyDocument: Missing required field Principal code example

Example: Error: Error Updating IAM Role (lambda_exec) Assume Role Policy: MalformedPolicyDocument: Missing required field Principal

# Error: Error Updating IAM Role (lambda_exec) Assume Role Policy: MalformedPolicyDocument: Missing required field Principal
Add this Principle below the Effect line.
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },