convert float to string numba python numpy array

I am running a @nb.njit function within which I am trying to put an integer within a string array.

import numpy as np
import numba as nb

@nb.njit(nogil=True)
def func():
    my_array = np.empty(6, dtype=np.dtype("U20"))
    my_array[0] = np.str(2.35646)
    return my_array


if __name__ == '__main__':
    a = func()
    print(a)

I am getting the following error :

numba.errors.TypingError: Failed in nopython mode pipeline (step: nopython frontend)
Invalid use of Function(<class 'str'>) with argument(s) of type(s): (float64)

Which function am I supposed to use to do the conversion from float to string within numba ?

from convert float to string numba python numpy array