code: def get_corner(self, time):
          
          if self.start_time <= time <= self.end_time:
              diff = time - self.start_time
              return self.i[diff][0, 0], self.j[diff][0, 0]
          else:
              return -1, -1
docs: Gets the corner array indices of the STObject at a given time that corresponds 
          to the upper left corner of the bounding box for the STObject.
  
          Args:
              time: time at which the corner is being extracted.
  
          Returns:
                corner index.