Time Based Key-Value Store

class TimeMap:
    def __init__(self):
        self.keyStore = {} # key : list of [val, timestamp]
        
    def set(self, key, value, timestamp):
        if key not in self.keyStore:
            self.keyStore[key] = []
        self.keyStore[key].append([value, timestamp])
        
    def get(self, key, timestamp):
        res = ""
        values = self.keyStore.get(key, [])
        l, r = 0, len(values) - 1
        
        while l <= r:
            m = (l + r) // 2
            if values[m][1] <= timestamp:
                res = values[m][0]
                l = m + 1
            else:
                r = m - 1
                
        return res