Compare two strings by comparing the sum of their values (ASCII character code).
* For comparing treat all letters as UpperCase
* `null/NULL/Nil/None` should be treated as empty strings
* If the string contains other characters than letters, treat the whole string as it would be empty
Your method should return `true`, if the strings are equal and `false` if they are not equal.
## Examples:
```
"AD", "BC"  -> equal
"AD", "DD"  -> not equal
"gf", "FG"  -> equal
"zz1", ""   -> equal (both are considered empty)
"ZzZz", "ffPFF" -> equal
"kl", "lz"  -> not equal
null, ""    -> equal
```
def compare(s1,s2):
    if not s1 or not all(map(str.isalpha, s1)):
        s1 = ''       
    if not s2 or not all(map(str.isalpha, s2)):
        s2 = ''
    return sum(map(ord, s1.upper())) == sum(map(ord, s2.upper()))
def compare(s1,s2):
    if not s1 or not all(map(str.isalpha, s1)):
        s1 = ''       
    if not s2 or not all(map(str.isalpha, s2)):
        s2 = ''
    return sum(map(ord, s1.upper())) == sum(map(ord, s2.upper()))