Implement a singly linked list with these methods:

class LinkedList:
    def append(self, val): ...   # Add to end
    def prepend(self, val): ...  # Add to front
    def delete(self, val): ...   # Delete first occurrence
    def to_list(self) -> list: ...  # Return as Python list

Example

ll = LinkedList()
ll.append(1); ll.append(2); ll.append(3)
ll.prepend(0)
ll.to_list() → [0, 1, 2, 3]
ll.delete(2)
ll.to_list() → [0, 1, 3]