Created by: Aurelius84

In this PR, we changed the way of inserting newly defined functionDef nodes into AST root.

Instead of inserting all the func_nodes into outer body of AST root, we used nested structure by adding func_nodes in front of the current if/else statement.

Pros:

• More clearly to understand the relationship between cond layer and true_func/false_func
• In some cases, it's easier to deal with the parameter self scope problem in Class. Because private variable with self can't be visited friendly if insert func_nodes into AST root.

Raw code::

def foo():
    if  control_flow_if:
        out= do_something
    else:
        out = do_nothing
    return out

Before this PR:

def true_func():
    return do_something

def false_func():
    return do_nothing

def foo():
    out = layers.cond(control_flow_if, true_func, false_func)
    return out

In this PR:

def foo():
    def true_func():
        return do_something

    def false_func():
        return do_nothing

    out = layers.cond(control_flow_if, true_func, false_func)
    return out