content: """
  Electron-phonon coupling self-energy
  ====================================
  
  A diagram containing loopy lines.
  """
  from feynman import Diagram
  import matplotlib.pyplot as plt
  
  fig = plt.figure(figsize=(8,2))
  ax = fig.add_axes([0,0,1,1], frameon=False)
  
  ax.set_xlim(0, fig.get_size_inches()[0])
  ax.set_ylim(0, fig.get_size_inches()[1])
  
  # Init D and ax
  D = Diagram(ax)
  
  D.x0 = 0.2
  D.y0 = sum(D.ax.get_ylim()) * .35
  
  # Various size
  opwidth = 1.
  linlen = 2.
  txtpad = .8
  wiggle_amplitude=.1
  
  # Line styles
  Ph_style = dict(style='elliptic loopy', ellipse_spread=.6, xamp=.10, yamp=-.15, nloops=15)
  DW_style = dict(style='circular loopy', circle_radius=.7, xamp=.10, yamp=.15, nloops=18)
  G_style = dict(style='simple', arrow=True, arrow_param={'width':0.15, 'length': .3})
  
  # Item 1
  v11 = D.vertex([D.x0, D.y0])
  v12 = D.vertex(v11.xy, dx=opwidth)
  Sigma = D.operator([v11, v12])
  Sigma.text("$\Sigma^{ep}$")
  
  # Symbol
  D.text(v12.x + txtpad, D.y0, "=")
  
  # Item 3
  v21 = D.vertex([v12.x + 2 * txtpad,  D.y0 - 0.3])
  v22 = D.vertex(v21.xy, dx=linlen)
  G = D.line(v21, v22, **G_style)
  Ph = D.line(v21, v22, **Ph_style)
  
  # Symbol
  D.text(v22.x + txtpad, D.y0, "+")
  
  # Item 3
  v31 = D.vertex([v22.x + 3 * txtpad,  D.y0 - 0.3])
  DW = D.line(v31, v31, **DW_style)
  
  D.plot()
  plt.show()
  