message: set greyblock to False by default in density
diff: @@ -361,7 +361,7 @@ def plot_persistence_density(
  legend=False,
  axes=None,
  fontsize=16,
  - greyblock=True
  + greyblock=False
  ):
  """This function plots the persistence density from persistence
  values list, np.array of shape (N x 2) representing a diagram
  @@ -410,7 +410,7 @@ def plot_persistence_density(
  :param fontsize: Fontsize to use in axis.
  :type fontsize: int
  :param greyblock: if we want to plot a grey patch on the lower half plane
  - for nicer rendering. Default True.
  + for nicer rendering. Default False.
  :type greyblock: boolean
  :returns: (`matplotlib.axes.Axes`): The axes on which the plot was drawn.
  """
  