Write a function to extract specified size of strings from a give list of string values.
def extract_string(str, l):
    result = [e for e in str if len(e) == l] 
    return result
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to extract specified size of strings from a give list of string values.
def extract_string(str, l):
    result = [e for e in str if len(e) == l] 
    return result[/INST]assert extract_string(['Python', 'list', 'exercises', 'practice', 'solution'] ,8)==['practice', 'solution']
assert extract_string(['Python', 'list', 'exercises', 'practice', 'solution'] ,6)==['Python']
assert extract_string(['Python', 'list', 'exercises', 'practice', 'solution'] ,9)==['exercises']</s>