code: def get_size(
              self,
              bucket: str,
              key: str
      ) -> int:
          
          blob_obj = self._get_blob_obj(bucket, key)
          return blob_obj.size
docs: Retrieves the filesize
          :param bucket: the bucket the object resides in.
          :param key: the key of the object for which size is being retrieved.
          :return: integer equal to filesize in bytes