Reset Stan model and all tracked distributions and parameters.

def reset(self):
        '''
        Reset Stan model and all tracked distributions and parameters.
        '''
        self.parameters = []
        self.transformed_parameters = []
        self.expressions = []
        self.data = []
        self.transformed_data = []
        self.X = {}
        self.model = []
        self.mu_cont = []
        self.mu_cat = []
        self._original_names = {}
        # variables to suppress in output. Stan uses limited set for variable
        # names, so track variable names we may need to simplify for the model
        # code and then sub back later.
        self._suppress_vars = ['yhat', 'lp__']