Write a method that takes a string as an argument and groups the number of time each character appears in the string as a hash sorted by the highest number of occurrences.
The characters should be sorted alphabetically e.g:
```python
get_char_count("cba") == {1: ["a", "b", "c"]}
```
You should ignore spaces, special characters and count uppercase letters as lowercase ones.
For example: 
```python
get_char_count("Mississippi")           ==  {4: ["i", "s"], 2: ["p"], 1: ["m"]}
get_char_count("Hello. Hello? HELLO!")  ==  {6: ["l"], 3: ["e", "h", "o"]}
get_char_count("aaa...bb...c!")         ==  {3: ["a"], 2: ["b"], 1: ["c"]}
get_char_count("abc123")                ==  {1: ["1", "2", "3", "a", "b", "c"]}
get_char_count("aaabbbccc")             ==  {3: ["a", "b", "c"]}
```
from collections import Counter, defaultdict
def get_char_count(s):
    d = defaultdict(list)
    c = Counter(sorted(s.lower()))
    for i,j in c.items():
        if i.isalnum() : d[j].append(i)
    return dict(sorted(d.items())[::-1])
from collections import Counter, defaultdict
def get_char_count(s):
    d = defaultdict(list)
    c = Counter(sorted(s.lower()))
    for i,j in c.items():
        if i.isalnum() : d[j].append(i)
    return dict(sorted(d.items())[::-1])