Update solution.py

./kyu_4/range_extraction/solution.py:12:1: W293 blank line contains whitespace
    """
    Solution for Range Extraction problem.

    Tt takes a list of integers in increasing order and returns
    a correctly formatted string in the range format.
    :param args: list
    :return: str
    """
^
./kyu_4/range_extraction/solution.py:41:19: W291 trailing whitespace
def case_3(a: int,
                  ^
./kyu_4/range_extraction/solution.py:42:26: W291 trailing whitespace
           current: list,
                         ^
./kyu_4/range_extraction/solution.py:46:1: W293 blank line contains whitespace
    """
    Case #3.

    :param a: int
    :param current: list
    :param result: str
    :return: str
    """
^
./kyu_4/range_extraction/solution.py:67:1: W293 blank line contains whitespace
    """
    Case #2.

    :return: str
    """

kyu_4/range_extraction/solution.py

@@ -9,7 +9,7 @@
 def solution(args: list) -> str:
     """
     Solution for Range Extraction problem.
-    
+
     Tt takes a list of integers in increasing order and returns
     a correctly formatted string in the range format.
     :param args: list
@@ -38,12 +38,12 @@ def solution(args: list) -> str:
     return result
 
 
-def case_3(a: int, 
-           current: list, 
+def case_3(a: int,
+           current: list,
            result: str) -> str:
     """
     Case #3.
-    
+
     :param a: int
     :param current: list
     :param result: str
@@ -64,7 +64,7 @@ def case_3(a: int,
 def case_2(**kwargs) -> str:
     """
     Case #2.
-    
+
     :return: str
     """
     a: int = kwargs['a']