I am trying to define a simple function which checks if what the user placed into the arguments equal the letter B (No reason. Just made it B.) This is my code:

```
def letter_check_B(letter):
    letter = str(letter)
    if letter == 'B':
        print("You entered B")
    else:
        print("You did not enter B")

```

However, when using the above code, by typing in: 

```
 letter_check_B(B)

```

I get an error stating: 

```
NameError: name 'B' is not defined

```

How would I go about to fix this without changing how the overall code works. I want to be able to make this code work by placing the letter into the argument (if that is possible).