'Drop redundant conversion nodes after tree changes.'

def visit_CoerceToBooleanNode(self, node):

    self.visitchildren(node)
    arg = node.arg
    if isinstance(arg, ExprNodes.PyTypeTestNode):
        arg = arg.arg
    if isinstance(arg, ExprNodes.CoerceToPyTypeNode):
        if (arg.type in (PyrexTypes.py_object_type, Builtin.bool_type)):
            return arg.arg.coerce_to_boolean(self.current_env())
    return node
