text: """
  ============================
  Draw flat objects in 3D plot
  ============================
  
  Demonstrate using pathpatch_2d_to_3d to 'draw' shapes and text on a 3D plot.
  """
  
  import numpy as np
  import matplotlib.pyplot as plt
  from matplotlib.patches import Circle, PathPatch
  from matplotlib.text import TextPath
  from matplotlib.transforms import Affine2D
  # This import registers the 3D projection, but is otherwise unused.
  from mpl_toolkits.mplot3d import Axes3D  # noqa: F401 unused import
  import mpl_toolkits.mplot3d.art3d as art3d
  
  
  def text3d(ax, xyz, s, zdir="z", size=None, angle=0, usetex=False, **kwargs):
      '''
      Plots the string 's' on the axes 'ax', with position 'xyz', size 'size',
      and rotation angle 'angle'.  'zdir' gives the axis which is to be treated
      as the third dimension.  usetex is a boolean indicating whether the string
      should be interpreted as latex or not.  Any additional keyword arguments
      are passed on to transform_path.
  
      Note: zdir affects the interpretation of xyz.
      '''
      x, y, z = xyz
      if zdir == "y":
          xy1, z1 = (x, z), y
      elif zdir == "x":
          xy1, z1 = (y, z), x
      else:
          xy1, z1 = (x, y), z
  
      text_path = TextPath((0, 0), s, size=size, usetex=usetex)
      trans = Affine2D().rotate(angle).translate(xy1[0], xy1[1])
  
      p1 = PathPatch(trans.transform_path(text_path), **kwargs)
      ax.add_patch(p1)
      art3d.pathpatch_2d_to_3d(p1, z=z1, zdir=zdir)
  
  
  fig = plt.figure()
  ax = fig.add_subplot(111, projection='3d')
  
  # Draw a circle on the x=0 'wall'
  p = Circle((5, 5), 3)
  ax.add_patch(p)
  art3d.pathpatch_2d_to_3d(p, z=0, zdir="x")
  
  # Manually label the axes
  text3d(ax, (4, -2, 0), "X-axis", zdir="z", size=.5, usetex=False,
         ec="none", fc="k")
  text3d(ax, (12, 4, 0), "Y-axis", zdir="z", size=.5, usetex=False,
         angle=np.pi / 2, ec="none", fc="k")
  text3d(ax, (12, 10, 4), "Z-axis", zdir="y", size=.5, usetex=False,
         angle=np.pi / 2, ec="none", fc="k")
  
  # Write a Latex formula on the z=0 'floor'
  text3d(ax, (1, 5, 0),
         r"$\displaystyle G_{\mu\nu} + \Lambda g_{\mu\nu} = "
         r"\frac{8\pi G}{c^4} T_{\mu\nu}  $",
         zdir="z", size=1, usetex=True,
         ec="none", fc="k")
  
  ax.set_xlim(0, 10)
  ax.set_ylim(0, 10)
  ax.set_zlim(0, 10)
  
  plt.show()
  