A Vector Class with Operator Overloading

Implement an immutable 2-D Vector(x, y) supporting:

• v + w, v - w, v * k and k * v (scalar), -v
• abs(v) (length) and v @ w (dot product)
• == with another Vector, and hashing (so vectors work in sets)
• repr(v) returning Vector(1, 2)
• iteration, so x, y = v works

Return NotImplemented from operators when the other operand has the wrong type.