input: Write a function to calculate the sum of squares of all numbers in a given array of integers. If the given array is empty then return 0.
  assert sum_squares([2, 3, 4])==29
  assert sum_squares([1, 2, 3])==14
  assert sum_squares([0, -1, -2])==5
  assert sum_squares([])==0
  assert sum_squares([5])==25
output: def sum_squares(arr):
      return sum(x**2 for x in arr)