code: def mat_to_numpy_arr(self):
    ''' convert list to numpy array - numpy arrays can not be saved as json '''
    import numpy as np
    self.dat['mat'] = np.asarray(self.dat['mat']f mat_to_numpy_arr(self):
    ''' convert list to numpy array - numpy arrays can not be saved as json '''
    import numpy as np
    self.dat['mat'] = np.asarray(self.dat['mat'])
docs: convert list to numpy array - numpy arrays can not be saved as json