docs: def getImgIds(self, imgIds=[], catIds=[]):
          '''
          Get img ids that satisfy given filter conditions.
          :param imgIds (int array) : get imgs for given ids
          :param catIds (int array) : get imgs with all given cats
          :return: ids (int array)  : integer array of img ids
          '''
          imgIds = imgIds if _isArrayLike(imgIds) else [imgIds]
          catIds = catIds if _isArrayLike(catIds) else [catIds]
  
          if len(imgIds) == len(catIds) == 0:
              ids = self.imgs.keys()
          else:
              ids = set(imgIds)
              for i, catId in enumerate(catIds):
                  if i == 0 and len(ids) == 0:
                      ids = set(self.catToImgs[catId])
                  else:
                      ids &= set(self.catToImgs[catId])
          return list(ids)