def min_item(self):
if self.is_empty():<EOL><INDENT>raise ValueError("<STR_LIT>")<EOL><DEDENT>node = self._root<EOL>while node.left is not None:<EOL><INDENT>node = node.left<EOL><DEDENT>return node.key, node.value<EOL>
Get item with min key of tree, raises ValueError if tree is empty.