def remove_sister(self, sister=None):
sisters = self.get_sisters()<EOL>if len(sisters) > <NUM_LIT:0>:<EOL><INDENT>if sister is None:<EOL><INDENT>sister = sisters.pop(<NUM_LIT:0>)<EOL><DEDENT>return self.up.remove_child(sister)<EOL><DEDENT>
Removes a sister node. It has the same effect as
**`TreeNode.up.remove_child(sister)`**

If a sister node is not supplied, the first sister will be deleted
and returned.

:argument sister: A node instance

:return: The node removed