code: def _lookup(self, timestamp):
          
  
          idx = search_greater(self._values, timestamp)
          if (idx < len(self._values)
                  and math.fabs(self._values[idx][0] - timestamp) < self.EPSILON):
              return idx
          return None
docs: Return the index of the value associated with "timestamp" if any, else
          None. Since the timestamps are floating-point values, they are
          considered equal if their absolute difference is smaller than
          self.EPSILON