code: def Lorentzian(x, a, x0, sigma, y0):
      
      return a / (1 + ((x - x0) / sigma) ** 2) + y0
docs: Lorentzian peak
  
      Inputs:
      -------
          ``x``: independent variable
          ``a``: scaling factor (extremal value)
          ``x0``: center
          ``sigma``: half width at half maximum
          ``y0``: additive constant
  
      Formula:
      --------
          ``a/(1+((x-x0)/sigma)^2)+y0``