Error while calling latt.k_to_n

There seems to be an issue while calling latt.k_to_n for valid values of k. The code and the error message is shown below:

latt = Lattice(item['Green_tau_lattice']) k = [np.pi, np.pi] n = latt.k_to_n(k)

Error_message : k not found [3.141592653589793, 3.141592653589793] [3.14159265 3.14159265] 2 2 -1 [2.0943951 2.0943951].

The function latt.k_to_n seems to work only for [0,0] and returns the above mentioned error for other values of k_vector.