Write a program that accepts a sentence and calculate the number of letters and digits.

1. Define function 'letterAndDigit' which will accept a string as argument.
2. String should not be empty or none.
3. Calculate number of digits and characters inside string and return a dict object in format of {"DIGITS":count, "LETTERS":count}.
4. Function should pass all test cases.

Instructions:

• Program should be written in file letter_digit.py

• Function name should be letterAndDigit.

• Input

   Type:  String
   Value: 'world! 234'
  

• Expected Output

    Type:  Dictionary
    Value: {'DIGITS' : 3, 'LETTERS' : 5}