Problem

Implement a stack using an array. The stack should support the following operations:

1. push(value: int): Adds value to the top of the stack.
2. pop(): Removes and returns the top value from the stack. If the stack is empty, return None.
3. peek(): Returns the top value without removing it. If the stack is empty, return None.
4. is_empty(): Returns True if the stack is empty, otherwise False.

Examples

Example 1:

stack = MyStack()
stack.push(1)
stack.push(2)
stack.peek()  # Output: 2
stack.pop()    # Output: 2
stack.is_empty()  # Output: False

Example 2:

stack = MyStack()
stack.pop()    # Output: None
stack.peek()   # Output: None
stack.is_empty()  # Output: True

Constraints

• The stack can hold up to 10^4 elements.
• The values pushed onto the stack will be integers within the range of [-10^9, 10^9].