Custom Queries doc might be wrong

**Describe the content issue**:
Hi Team! I'm trying to use the Custom Queries, to make BatchPut on Dynamo, I've followed the example in the doc: https://docs.amplify.aws/flutter/build-a-backend/data/custom-business-logic/batch-ddb-operations/
At the end of the example
```
const { data, errors } = await client.mutations.BatchCreatePost({
contents: ['Post 1', 'Post 2', 'Post 3']
});
```
There is a client, but for the rest of examples there is no "client" it's only
```
final request = ModelMutations.create(todo);
final response = await Amplify.API.mutate(request: request).response;
```

this seems to be a Typescript example in the flutter section.

**URL page where content issue is**:
https://docs.amplify.aws/flutter/build-a-backend/data/custom-business-logic/batch-ddb-operations/