Implement simple VM manager with CRUD operations

You are asked to implement a simple in-memory virtual machine (VM) manager that can:

• List all VMs
• Add (create) a new VM
• Modify (update) an existing VM
• Delete an existing VM

Each VM has a set of attributes. For this exercise, you can assume at least the following attributes:

• id (string or integer, must be unique )
• name (string)
• cpu_cores (integer)
• memory_gb (integer)
• status (string, e.g., "running" , "stopped" )

Requirements

1. Data model & storage
   • Choose an appropriate in-memory data structure to store the VMs.
   • Ensure id is treated as the unique identifier for each VM.
2. API / Interface Design and implement a small API (in the language of your choice) with at least the following operations:
   • create_vm(vm)
     • Input: VM attributes (including id ).
     • Behavior: Adds a new VM to the manager.
   • list_vms()
     • Input: none.
     • Output: a collection/list of all VMs currently stored.
   • update_vm(id, updated_fields)
     • Input: the id of the VM to update, and a set/dictionary of fields to update.
     • Behavior: Modifies the attributes of the existing VM with the given id .
   • delete_vm(id)
     • Input: the id of the VM to delete.
     • Behavior: Removes the VM with the given id from the manager.
3. Error handling
   • If create_vm is called with an id that already exists, you must detect this and handle it as an error.
   • If update_vm or delete_vm is called with an id that does not exist, you must detect this and handle it as an error.
   • Define clearly how errors are surfaced (e.g., exceptions, error codes, or special return values) and keep it consistent across methods.
4. Complexity considerations
   • Aim for efficient average-time operations for lookup, update, and delete by id .

Explain your design choices (data structures and API shape) in brief comments or docstrings within your code.