I'm trying to learn Python through Learn Python the Hard Way. I'm now on Exercise 39 and have a simple question. I tried to search online but couldn't find any answers. Here's the code from the exercise:

```
# create a mapping of state to abbreviation
states = {
    'Oregon': 'OR',
    'Florida': 'FL',
    'California': 'CA',
    'New York': 'NY',
    'Michigan': 'MI'
}

# create a basic set of states and some cities in them
cities = {
    'CA': 'San Francisco',
    'MI': 'Detroit',
    'FL': 'Jacksonville'
}

print '-' * 10
# safely get a abbreviation by state that might not be there
state = states.get('Texas', None)

if not state:
    print "Sorry, no Texas."

# get a city with a default value
city = cities.get('TX', 'Does Not Exist')
print "The city for the state 'TX' is: %s" % city

```

I don't quite understand what `None` does in `state = states.get('Texas', None)`. If it were used to tell Python that "there is no more," then why couldn't I just write `state = states.get('Texas')`? What do I need the extra `None` here? Thanks!