input: Write a python function to calculate the roots of a quadratic equation.
  assert calculate_roots(1, -7, 12) == ((3+0j), (4+0j))
  assert calculate_roots(1, -3, 2) == ((1+0j), (2+0j))
  assert calculate_roots(1, 2, 1) == ((-1+0j), (-1+0j))
output: def calculate_roots(a, b, c):
      import cmath
      d = b**2 - 4*a*c
      root1 = (-b + cmath.sqrt(d)) / (2*a)
      root2 = (-b - cmath.sqrt(d)) / (2*a)
      return (root1, root2)