input: Write a function to optimize a given multivariate function using SciPy's optimization module. The function should take two parameters: the first is the function to be optimized and the second is the initial guess for the optimization. The function should return the optimized values of the variables.
  
  assert (optimize_function(lambda x: x[0]**2 + x[1]**2, [2, 3]) == [0, 0]).all()
  assert (optimize_function(lambda x: (x[0]-1)**2 + (x[1]+2)**2, [0, 0]) == [1, -2]).all()
output: def optimize_function(func, initial_guess):
      from scipy.optimize import minimize
      result = minimize(func, initial_guess)
      return result.x