interface IData {
  snake_id?: number;
  user_snake?: {
    first_name: string;
    last_name: string;
  };
  userCamel?: {
    firstName: string;
    lastName: string;
    snake_name: string;
  };
}

const data: IData = {};

// RIGHT: No problem when accessing CamelCase fields
console.log('CamelFirstName:', data.userCamel?.firstName);

// RIGHT: No problem when accessing snake_case's fields methods
console.log('CamelFirstName:', data.snake_id?.toString());

// WRONG: Error when accessing snake_case fields after optional chaining operator
console.log('snake_first_name:', data.user_snake?.first_name);
console.log('snake_first_name:', data.userCamel?.snake_name);