message: Ignore figure as not used on default subplot
diff: @@ -168,7 +168,7 @@ def plot_persistence_barcode(
  if colormap == None:
  colormap = plt.cm.Set1.colors
  if axes == None:
  - fig, axes = plt.subplots(1, 1)
  + _, axes = plt.subplots(1, 1)
  persistence = sorted(persistence, key=lambda birth: birth[1][0])
  @@ -307,7 +307,7 @@ def plot_persistence_diagram(
  if colormap == None:
  colormap = plt.cm.Set1.colors
  if axes == None:
  - fig, axes = plt.subplots(1, 1)
  + _, axes = plt.subplots(1, 1)
  (min_birth, max_death) = __min_birth_max_death(persistence, band)
  delta = (max_death - min_birth) * inf_delta
  @@ -487,7 +487,7 @@ def plot_persistence_density(
  if cmap is None:
  cmap = plt.cm.hot_r
  if axes == None:
  - fig, axes = plt.subplots(1, 1)
  + _, axes = plt.subplots(1, 1)
  # line display of equation : birth = death
  x = np.linspace(death.min(), birth.max(), 1000)
  