def leftsibling(node):
if node.parent:<EOL><INDENT>pchildren = node.parent.children<EOL>idx = pchildren.index(node)<EOL>if idx:<EOL><INDENT>return pchildren[idx - <NUM_LIT:1>]<EOL><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT>
Return Left Sibling of `node`.

>>> from anytree import Node
>>> dan = Node("Dan")
>>> jet = Node("Jet", parent=dan)
>>> jan = Node("Jan", parent=dan)
>>> joe = Node("Joe", parent=dan)
>>> leftsibling(dan)
>>> leftsibling(jet)
>>> leftsibling(jan)
Node('/Dan/Jet')
>>> leftsibling(joe)
Node('/Dan/Jan')