nr.seed(2021)
from math import pi
def seasonal_ts(start = '1-1990', end = '1-2021', freq = 'M', slope = 0.02, sd = 1.0, mean = 0):
    dates = pd.date_range(start = start, end = end, freq = freq)
# trend component
    seasonal = pd.Series([slope*x for x in range(len(dates))],
                    index = dates)
# noise component
    seasonal = seasonal + nr.normal(loc = mean, scale = sd, size = len(dates))