Appwrite Server API Missing required attribute

Question

Using Appwrite with Flutter Unhandled Exception: AppwriteException: document_invalid_structure, Invalid document structure: Missing required attribute "sender_name"

Unable to use Appwrite Server API as it gives this error

I was trying to make a chat app and encountered this error when I tried to use Server API to progmatically create collection

if (collection.attributes.isEmpty) {
      await _defineDocument(collection.$id);
    }
    // Return the collection id
    return collection.$id;
  }
Future<void> _defineDocument(String collectionId) async {
    // Defining attributes
    try {
      // You are free to choose your own key name.
      // But make to sure to replace those things in the model too.
      await database.createStringAttribute(
          databaseId: AppwriteConstants.databaseId,
          collectionId: collectionId,
          key: "sender_name",
          size: 255,
          xrequired: true);

wrote similar code for other attributes as well

When I go to appwrite console, it does show that these attributes are created...but gives the error that the required attribute is missing (with the same name as you can see) [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: AppwriteException: document_invalid_structure, Invalid document structure: Missing required attribute "sender_name" (400)