code: def DSYR_numpy(A, x, alpha=1.):
      
      A += alpha * np.dot(x[:, None], x[None, :])
docs: Performs a symmetric rank-1 update operation:
      A <- A + alpha * np.dot(x,x.T)
  
      :param A: Symmetric NxN np.array
      :param x: Nx1 np.array
      :param alpha: scalar