code: def get_sigma(imt):
      
      if imt.period < 0.2:
          return np.log(10**0.23)
      elif imt.period > 1.0:
          return np.log(10**0.27)
      else:
          return np.log(10**(0.23 + (imt.period - 0.2)/0.8 * 0.04))
docs: Return the value of the total sigma
  
      :param float imt:
          An :class:`openquake.hazardlib.imt.IMT` instance
      :returns:
          A float representing the total sigma value