input: Write a python function to evaluate a polynomial at a given point using the Polynomial class.
  assert Polynomial([1, 2, 3])(2) == 17
  assert Polynomial([0, 0, 1])(3) == 9
  assert Polynomial([5, 0, -1])(1) == 4
output: class Polynomial:
      def __init__(self, coefficients):
          self.coefficients = coefficients
  
      def __call__(self, x):
          return sum(coef * (x ** i) for i, coef in enumerate(self.coefficients))