Bank Account Encapsulation

Implement a BankAccount class that demonstrates encapsulation with business rules.

Requirements:

• The constructor accepts an account holder name and an optional starting balance.
• The balance must be internal/private state.
• Provide deposit(amount), withdraw(amount), and getBalance() methods.
• deposit(amount) increases the balance by a positive amount and returns the updated balance.
• withdraw(amount) decreases the balance by a positive amount only if sufficient funds exist; it returns True on success; otherwise it leaves the balance unchanged and returns False.
• getBalance() returns the current balance.
• Invalid amounts (0 or negative) must raise an error (ValueError in Python).
• The starting balance must also be non-negative.

Examples:

alice = BankAccount("Alice", 500)
alice.withdraw(150)  # True
alice.getBalance()   # 350

acct = BankAccount("Ben", 100)
acct.withdraw(150)  # False, balance stays 100