def set_arrowstyle(self, arrowstyle=None, **kw):
if arrowstyle==None:<EOL><INDENT>return ArrowStyle.pprint_styles()<EOL><DEDENT>if isinstance(arrowstyle, ConnectionStyle._Base):<EOL><INDENT>self._arrow_transmuter = arrowstyle<EOL><DEDENT>else:<EOL><INDENT>self._arrow_transmuter = ArrowStyle(arrowstyle, **kw)<EOL><DEDENT>
Set the arrow style.

*arrowstyle* can be a string with arrowstyle name with optional
 comma-separated attributes. Alternatively, the attrs can
 be provided as keywords.

 set_arrowstyle("Fancy,head_length=0.2")
 set_arrowstyle("fancy", head_length=0.2)

Old attrs simply are forgotten.

Without argument (or with arrowstyle=None), return
available box styles as a list of strings.