(self, node)
:returns: index of the node in the children array or ``None`` if it's not a child
:returns: index of the node in the children array or ``None`` if it's not a child
: returns : index of the node in the children array or None if it s not a child
def indexof(self, node):
        """
        :returns: index of the node in the children array or ``None`` if it's not a child
        """
        if node in self.children:
            return self.children.index(node)
        else:
            return None
def indexof ( self , node ) : if node in self . children : return self . children . index ( node ) else : return None