# project-08a

Write a Python function called count_letters that takes a string as a parameter and returns a dictionary that tabulates how many of each letter is in that string.  
The string can contain characters other than letters, empty string, lower and upper-case letter, but the function should only count letter and only count once regardless of upper-case or lower-case.  
The keys of the dictionary should be upper-case letters.  
For example, if the string is
```
"AaBb"
```
then the dictionary that is returned should contain these key-value pairs:
```
{'A': 2, 'B': 2}
```

we haven't covered the build-in function isalpha() , so don't use it.

The file should be named: count_letters.py
