docs: def plot_net(fignum):
      """
      Draws circle and tick marks for equal area projection.
      """
  
  # make the perimeter
      plt.figure(num=fignum,)
      plt.clf()
      plt.axis("off")
      Dcirc = np.arange(0, 361.)
      Icirc = np.zeros(361, 'f')
      Xcirc, Ycirc = [], []
      for k in range(361):
          XY = pmag.dimap(Dcirc[k], Icirc[k])
          Xcirc.append(XY[0])
          Ycirc.append(XY[1])
      plt.plot(Xcirc, Ycirc, 'k')
  
  # put on the tick marks
      Xsym, Ysym = [], []
      for I in range(10, 100, 10):
          XY = pmag.dimap(0., I)
          Xsym.append(XY[0])
          Ysym.append(XY[1])
      plt.plot(Xsym, Ysym, 'k+')
      Xsym, Ysym = [], []
      for I in range(10, 90, 10):
          XY = pmag.dimap(90., I)
          Xsym.append(XY[0])
          Ysym.append(XY[1])
      plt.plot(Xsym, Ysym, 'k+')
      Xsym, Ysym = [], []
      for I in range(10, 90, 10):
          XY = pmag.dimap(180., I)
          Xsym.append(XY[0])
          Ysym.append(XY[1])
      plt.plot(Xsym, Ysym, 'k+')
      Xsym, Ysym = [], []
      for I in range(10, 90, 10):
          XY = pmag.dimap(270., I)
          Xsym.append(XY[0])
          Ysym.append(XY[1])
      plt.plot(Xsym, Ysym, 'k+')
      for D in range(0, 360, 10):
          Xtick, Ytick = [], []
          for I in range(4):
              XY = pmag.dimap(D, I)
              Xtick.append(XY[0])
              Ytick.append(XY[1])
          plt.plot(Xtick, Ytick, 'k')
      plt.axis("equal")
      plt.axis((-1.05, 1.05, -1.05, 1.05))