code: def acovf_ma1(ma):
      # MA(1)
      # from Greene p616 (with typo), Florens p280
      b = -ma[1]
      rho = np.zeros(10)
      rho[0] = 1 + b**2
      rho[1] = -b
      return rho
  
imports: import numpy
  from numpy.testing import assert_array_almost_equal
  import matplotlib.pyplot
  from statsmodels import regression
  from statsmodels.tsa.arima_process import arma_generate_sample, arma_impulse_response
  from statsmodels.tsa.arima_process import arma_acovf, arma_acf
  from statsmodels.tsa.arima.model import ARIMA
  from statsmodels.tsa.stattools import acf, acovf
  from statsmodels.graphics.tsaplots import plot_acf
label_desc: Use image node_id 9 for calling a global function with example usage: acovf_ma1(ma) and returns: rho