Let's assume we need "clean" strings. Clean means a string should only contain letters `a-z`, `A-Z` and spaces. We assume that there are no double spaces or line breaks.

Write a function that takes a string and returns a string without the unnecessary characters.

### Examples

```python
remove_chars('.tree1')    ==> 'tree'

remove_chars("that's a pie$ce o_f p#ie!")  ==> 'thats a piece of pie'

remove_chars('john.dope@dopington.com')    ==> 'johndopedopingtoncom'

remove_chars('my_list = ["a","b","c"]')    ==> 'mylist  abc'

remove_chars('1 + 1 = 2')    ==> '    ' (string with 4 spaces)

remove_chars("0123456789(.)+,|[]{}=@/~;^$'<>?-!*&:#%_")  ==> '' (empty string)
```

Difficulty: EASY
Starter code: def remove_chars(s):
	

Solutions:
import re

def remove_chars(s):
	return re.sub('[^a-zA-Z ]', '', s)


def remove_chars(s):
	return ''.join((c for c in s if c.isalpha() or c == ' '))


import re

def remove_chars(s):
	return re.sub('[^A-Za-z\\s]', '', s)


def remove_chars(s):
	return ''.join(list((i for i in s if i.isalpha() or i.isspace())))


import re

def remove_chars(s):
	return re.sub('(?i)[^a-z ]', '', s)


import re
remove_chars = lambda s: re.sub('[^a-z A-Z]', '', s)


import re
remove_chars = lambda s: re.sub('[^a-zA-Z\\ ]', '', s)


def remove_chars(s):
	w = ''
	for c in s:
		if c.isalpha() or c == ' ':
			w += c
	return w


def remove_chars(s):
	letters = 'abcdefghijklmnopqrstuvwxyz '
	return ''.join([i for i in s if i in letters or i in letters.upper()])


import re

def remove_chars(s):
	s = re.sub('\\W+', ' ', re.sub('[^A-Za-z]+', '', re.sub('[\\s]', 'SSSSSSSSSS', s)))
	return re.sub('[S]{10}', ' ', s)


def remove_chars(s):
	for x in s:
		if x != ' ':
			if not x.isalpha():
				s = s.replace(x, '')
	return s


import re

def remove_chars(string):
	pattern = '[^a-zA-Z\\s]'
	newstr = re.sub(pattern, '', string)
	return newstr


def remove_chars(s):
	import string
	return ''.join((c for c in s if c == ' ' or c in string.ascii_letters))


def remove_chars(s):
	ret = ''
	for c in s:
		if c.isalpha() or c is ' ':
			ret += c
	return ret