Minimum Window Substring

from collections import Counter
class Solution:
    def minWindow(self, s, t):
            if len(t) > len(s):
                return ""
            minLength = len(s) + 1
            count_t = Counter(t)
            distincts = len(count_t) #Number of distinct characters in "t"

            l,r = 0,0 #Pointers for the sliding window
            
            # Keep the starting and ending index of the smallest window
            minI = -1
            minJ = -1
            
            
            while r < len(s):
                if s[r] in count_t:
                    count_t[s[r]] -= 1
                    if count_t[s[r]] == 0: 
                        distincts -= 1
                
                while distincts == 0:
                    if r - l + 1 < minLength:
                        minLength = r - l + 1
                        minI = l
                        minJ = r
                    if s[l] in count_t: 
                        count_t[s[l]] += 1
                        if count_t[s[l]] == 1: 
                            distincts += 1
                    
                    l += 1
                r += 1
            
            substring = s[minI:minJ + 1]           
            return substring