change functools.cache to lru_cache (sony#1221)

model_compression_toolkit/trainable_infrastructure/pytorch/util.py

@@ -12,13 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
-from functools import cache
+from functools import lru_cache
 from typing import Callable
 
 from tqdm import tqdm
 
 
-@cache
+@lru_cache
 def get_total_grad_steps(representative_data_gen: Callable) -> int:
     # dry run on the representative dataset to count number of batches
     num_batches = 0