def save(self):
        tmp_path = self.path + '.tmp'
        with open(tmp_path, 'w') as f:
            f.write(json.dumps(self.body_labels.items()))
        os.rename(tmp_path, self.path)
def airgap(airgap, ax=0):
    """creates plot of flux density in airgap"""
    if ax == 0:
        ax = plt.gca()
    ax.set_title('Airgap Flux Density [T]')
    ax.plot(airgap['pos'], airgap['B'],
            label='Max {:4.2f} T'.format(max(airgap['B'])))
    ax.plot(airgap['pos'], airgap['B_fft'],
            label='Base Ampl {:4.2f} T'.format(airgap['Bamp']))
    ax.set_xlabel('Position/°')
    ax.legend()
    ax.grid(True)