Question: `node_name` is a string. Shouldn't this return a list of keys in the node\_list dictionary, which can be iterated over? Why does the error say it is not iterable?

```
class Graph:

def __init__(self):
    self.node_list = {}
    self.number = 0

def node(self, node_name):
    if node_name in self.node_list.keys: 
    ...

File "PythonProject2.3.py", line 10, in node
    if node_name in self.node_list.keys: #returns list of keys
TypeError: argument of type 'builtin_function_or_method' is not iterable

```

Answer: 
`.keys` is a function, not a property. Try this instead:

```
if node_name in self.node_list.keys():

```

A dictionary iterates over its keys by default, though, so this will work, too:

```
if node_name in self.node_list:

```
Please change 

```
if node_name in self.node_list.keys(): 

```

to 

```
if self.node_list.has_key(node_name):

```