Load
        Load data from file
    Inputs  : 
        path :
            specifies the path name of the file to be loaded from

def load(self, path="chain.dat"):
        """
    Load
        Load data from file
    Inputs  : 
        path :
            specifies the path name of the file to be loaded from
        """
        # read data from file
        file = open(path, 'r')
        dic = json.load(file)
        file.close()

        # get data from dictionary
        self._chain = np.array(dic['chain'])
        self._step_count = np.array(dic['step_count'])
        self._n_samples = dic['n_samples']
        self._n_accepted = dic['n_accepted']
        self._X = {}
        self._X['x'] = dic['x']
        self._X['f'] = dic['f']
        self._X['J'] = dic['J']