dynamodb query: ValidationException: The number of conditions on the keys is invalid

I have the following schema where I am basically just trying to have a table with id as primary key, and both code and secondCode to be global secondary indexes to use to query the table.

resource "aws_dynamodb_table" "myDb" {
  name         = "myTable"
  billing_mode = "PAY_PER_REQUEST"
  hash_key     = "id"

  attribute {
    name = "id"
    type = "S"
  }

  attribute {
    name = "code"
    type = "S"
  }

  attribute {
    name = "secondCode"
    type = "S"
  }

  global_secondary_index {
    name = "code-index" 
    hash_key = "code"
    projection_type = "ALL"
  }

  global_secondary_index {
    name = "second_code-index" 
    hash_key = "secondCode"
    projection_type = "ALL"
  }
}

When I try to look for one item by code

const toGet = Object.assign(new Item(), {
    code: 'code_456',
});

item = await dataMapper.get<Item>(toGet);

locally I get

ValidationException: The number of conditions on the keys is invalid

and on the deployed instance of the DB I get

The provided key element does not match the schema

I can see from the logs that the key is not being populated

Serverless: [AWS dynamodb 400 0.082s 0 retries] getItem({ TableName: 'myTable', Key: {} })

Here is the class configuration for Item

@table(getEnv('MY_TABLE'))
export class Item {
    @hashKey({ type: 'String' })
    id: string;

    @attribute({
        indexKeyConfigurations: { 'code-index': 'HASH' },
        type: 'String',
    })
    code: string;

    @attribute({
        indexKeyConfigurations: { 'second_code-index': 'HASH' },
        type: 'String',
    })
    secondCode: string;

    @attribute({ memberType: embed(NestedItem) })
    nestedItems?: Array<NestedItem>;
}

class NestedItem {
    @attribute()
    name: string;
    @attribute()
    price: number;
}

I am using https://github.com/awslabs/dynamodb-data-mapper-js