input: Write a function to optimize a given multivariate function using the scipy.optimize module. The function should take two arguments: the function to be optimized and an 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, [1, 1])==[0.0, 0.0]
output: def optimize_function(func, initial_guess):
      from scipy.optimize import minimize
      result = minimize(func, initial_guess)
      return result.x