code: def lmfit_parameter_values(self, params):
          
          return tuple( params[key].value for key in sorted(params) )
docs: `params` is a [`lmfit.Parameters`][1] object.
  
          Returns a tuple containing the values of the parameters in `params`.
  
          The order is determined by sorting the parameter keys alphabetically.
  
          [1]: http://lmfit.github.io/lmfit-py/parameters.html#the-parameters-class