code: def initial_trend(series, slen):
      sum = 0.0
      for i in range(slen):
          sum += float(series[i + slen] - series[i]) / slen
      return sum / slen
  
imports: import pandas
  import numpy
  import statsmodels.api
  from scipy import signal, integrate
  from pykalman import UnscentedKalmanFilter
  from tsaug import *
  from fbprophet import Prophet
  import pylab
  from seasonal.periodogram import periodogram
label_desc: Use image node_id 8 for calling a global function with example usage: initial_trend(series, slen) and returns: unknown