update group_by_date location within dolphin

src/sweets/core.py

@@ -8,9 +8,10 @@
 import h5py
 import numpy as np
 from dolphin import io, stitching, unwrap
+from dolphin._dates import group_by_date
 from dolphin._types import Bbox
 from dolphin.interferogram import Network
-from dolphin.utils import group_by_date, set_num_threads
+from dolphin.utils import set_num_threads
 from dolphin.workflows.config import YamlModel
 from opera_utils import group_by_burst
 from pydantic import ConfigDict, Field, field_validator, model_validator