mu: float or array_like of floats
    sigma: float or array_like of floats
    q: sample step
    random_state: an object of numpy.random.RandomState

def qlognormal(mu, sigma, q, random_state):
    '''
    mu: float or array_like of floats
    sigma: float or array_like of floats
    q: sample step
    random_state: an object of numpy.random.RandomState
    '''
    return np.round(lognormal(mu, sigma, random_state) / q) * q