>>> """
================================
Annotation arrow style reference
================================

Overview of the arrow styles available in `~.Axes.annotate`.
"""
... 
... import inspect
... import re
... import itertools
... 
... import matplotlib.patches as mpatches
... import matplotlib.pyplot as plt
... 
... styles = mpatches.ArrowStyle.get_styles()
... ncol = 2
... nrow = (len(styles) + 1) // ncol
... axs = (plt.figure(figsize=(4 * ncol, 1 + nrow))
...        .add_gridspec(1 + nrow, ncol,
...                      wspace=.7, left=.1, right=.9, bottom=0, top=1).subplots())
... for ax in axs.flat:
...     ax.set_axis_off()
... for ax in axs[0, :]:
...     ax.text(0, .5, "arrowstyle",
...             transform=ax.transAxes, size="large", color="tab:blue",
...             horizontalalignment="center", verticalalignment="center")
...     ax.text(.35, .5, "default parameters",
...             transform=ax.transAxes,
...             horizontalalignment="left", verticalalignment="center")
... for ax, (stylename, stylecls) in zip(axs[1:, :].T.flat, styles.items()):
...     l, = ax.plot(.25, .5, "ok", transform=ax.transAxes)
...     ax.annotate(stylename, (.25, .5), (-0.1, .5),
...                 xycoords="axes fraction", textcoords="axes fraction",
...                 size="large", color="tab:blue",
...                 horizontalalignment="center", verticalalignment="center",
...                 arrowprops=dict(
...                     arrowstyle=stylename, connectionstyle="arc3,rad=-0.05",
...                     color="k", shrinkA=5, shrinkB=5, patchB=l,
...                 ),
...                 bbox=dict(boxstyle="square", fc="w"))
...     # wrap at every nth comma (n = 1 or 2, depending on text length)
...     s = str(inspect.signature(stylecls))[1:-1]
...     n = 2 if s.count(',') > 3 else 1
...     ax.text(.35, .5,
...             re.sub(', ', lambda m, c=itertools.count(1): m.group()
...                    if next(c) % n else '\n', s),
...             transform=ax.transAxes,
...             horizontalalignment="left", verticalalignment="center")
... 
... plt.show()
... 
... #############################################################################
... #
... # .. admonition:: References
... #
... #    The use of the following functions, methods, classes and modules is shown
... #    in this example:
... #
... #    - `matplotlib.patches`
... #    - `matplotlib.patches.ArrowStyle`
... #    - ``matplotlib.patches.ArrowStyle.get_styles``
... #    - `matplotlib.axes.Axes.annotate`
...