How to use the flake8.util.ast function in flake8

late_decoration[meth.id] = func_name

        # iterate over all functions and tag them
        for node in iter_child_nodes(cls_node):
            if not isinstance(node, ast.FunctionDef):
                continue

            node.function_type = 'method'
            if node.name == '__new__':
                node.function_type = 'classmethod'

            if node.name in late_decoration:
                node.function_type = late_decoration[node.name]
            elif node.decorator_list:
                names = [d.id for d in node.decorator_list
                         if isinstance(d, ast.Name) and
                         d.id in ('classmethod', 'staticmethod')]
                if names:
                    node.function_type = names[0]

def get_code_complexity(code, threshold=7, filename='stdin'):
    try:
        tree = compile(code, filename, "exec", ast.PyCF_ONLY_AST)
    except SyntaxError:
        e = sys.exc_info()[1]
        sys.stderr.write("Unable to parse %s: %s\n" % (filename, e))
        return 0

    complx = []
    McCabeChecker.max_complexity = threshold
    for lineno, offset, text, check in McCabeChecker(tree, filename).run():
        complx.append(dict(
            type=McCabeChecker._code,
            lnum=lineno,
            text=text,
        ))

    return complx

def _unpack_args(args):
        ret = []
        for arg in args:
            if isinstance(arg, ast.Tuple):
                ret.extend(_unpack_args(arg.elts))
            else:
                ret.append(arg.id)
        return ret

def main(argv=None):
    if argv is None:
        argv = sys.argv[1:]
    opar = optparse.OptionParser()
    opar.add_option("-d", "--dot", dest="dot",
                    help="output a graphviz dot file", action="store_true")
    opar.add_option("-m", "--min", dest="threshold",
                    help="minimum complexity for output", type="int",
                    default=1)

    options, args = opar.parse_args(argv)

    with open(args[0], "rU") as mod:
        code = mod.read()
    tree = compile(code, args[0], "exec", ast.PyCF_ONLY_AST)
    visitor = PathGraphingAstVisitor()
    visitor.preorder(tree, visitor)

    if options.dot:
        print('graph {')
        for graph in visitor.graphs.values():
            if (not options.threshold or
                    graph.complexity() >= options.threshold):
                graph.to_dot()
        print('}')
    else:
        for graph in visitor.graphs.values():
            if graph.complexity() >= options.threshold:
                print(graph.name, graph.complexity())

def main(argv):
    opar = optparse.OptionParser()
    opar.add_option("-d", "--dot", dest="dot",
                    help="output a graphviz dot file", action="store_true")
    opar.add_option("-m", "--min", dest="threshold",
                    help="minimum complexity for output", type="int",
                    default=2)

    options, args = opar.parse_args(argv)

    with open(args[0], "rU") as mod:
        code = mod.read()
    tree = compile(code, args[0], "exec", ast.PyCF_ONLY_AST)
    visitor = PathGraphingAstVisitor()
    visitor.preorder(tree, visitor)

    if options.dot:
        print('graph {')
        for graph in visitor.graphs.values():
            if graph.complexity() >= options.threshold:
                graph.to_dot()
        print('}')
    else:
        for graph in visitor.graphs.values():
            if graph.complexity() >= options.threshold:
                print(graph.name, graph.complexity())

def get_code_complexity(code, min_complexity=7, filename='stdin'):
    try:
        tree = compile(code, filename, "exec", ast.PyCF_ONLY_AST)
    except SyntaxError:
        e = sys.exc_info()[1]
        sys.stderr.write("Unable to parse %s: %s\n" % (filename, e))
        return 0

    complx = []
    McCabeChecker.max_complexity = min_complexity
    for lineno, offset, text, check in McCabeChecker(tree, filename).run():
        complx.append('%s:%d:1: %s' % (filename, lineno, text))

    if len(complx) == 0:
        return 0
    print('\n'.join(complx))
    return len(complx)

def tag_class_functions(self, cls_node):
        """Tag functions if they are methods, classmethods, staticmethods"""
        # tries to find all 'old style decorators' like
        # m = staticmethod(m)
        late_decoration = {}
        for node in iter_child_nodes(cls_node):
            if not (isinstance(node, ast.Assign) and
                    isinstance(node.value, ast.Call) and
                    isinstance(node.value.func, ast.Name)):
                continue
            func_name = node.value.func.id
            if func_name in ('classmethod', 'staticmethod'):
                meth = (len(node.value.args) == 1 and node.value.args[0])
                if isinstance(meth, ast.Name):
                    late_decoration[meth.id] = func_name

        # iterate over all functions and tag them
        for node in iter_child_nodes(cls_node):
            if not isinstance(node, ast.FunctionDef):
                continue

            node.function_type = 'method'
            if node.name == '__new__':

def tag_class_functions(self, cls_node):
        """Tag functions if they are methods, classmethods, staticmethods"""
        # tries to find all 'old style decorators' like
        # m = staticmethod(m)
        late_decoration = {}
        for node in iter_child_nodes(cls_node):
            if not (isinstance(node, ast.Assign) and
                    isinstance(node.value, ast.Call) and
                    isinstance(node.value.func, ast.Name)):
                continue
            func_name = node.value.func.id
            if func_name in ('classmethod', 'staticmethod'):
                meth = (len(node.value.args) == 1 and node.value.args[0])
                if isinstance(meth, ast.Name):
                    late_decoration[meth.id] = func_name

        # iterate over all functions and tag them
        for node in iter_child_nodes(cls_node):
            if not isinstance(node, ast.FunctionDef):
                continue

            node.function_type = 'method'
            if node.name == '__new__':
                node.function_type = 'classmethod'

def visit_node(self, node):
        if isinstance(node, ast.ClassDef):
            self.tag_class_functions(node)
        elif isinstance(node, ast.FunctionDef):
            self.find_global_defs(node)

        method = 'visit_' + node.__class__.__name__.lower()
        for visitor in self.visitors:
            if not hasattr(visitor, method):
                continue
            for error in getattr(visitor, method)(node, self.parents):
                yield error