docs: def plotallanvar(data, dt, tmax=10, ax=None, **kwargs):
      """Plot Allan variance.
  
      Args:
          data (np.ndarray): Input data.
          dt (float): Time between each data.
          tmax (float): Maximum time.
          ax (matplotlib.axes): Axis the figure is plotted on.
          kwargs (optional): Plot options passed to ax.plot().
      """
      if ax is None:
          ax = plt.gca()
      tk, allanvar = allan_variance(data, dt, tmax)
      ax.loglog(tk, allanvar, **kwargs)
      ax.set_xlabel('Time [s]')
      ax.set_ylabel('Allan Variance')
      ax.legend()