add base and signal

Former-commit-id: 828ea0f0c3348532c794417d6714d279576a3291

core/io/base.py

+import h5py
+
+
+class BridgeH5:
+    def __init__(self, file):
+        self._hdf = h5py.File(file, "r")
+
+    def close(self):
+        self._hdf.close()

core/io/signal.py

+from postprocessor.core.io.base import BridgeH5
+
+
+class Signal(BridgeH5):
+    """
+    Class that fetches data from the hdf5 storage for post-processing
+    """
+
+    def __init__(self, file):
+        super().__init__(file)
+
+    def __getitem__(self, dataset):
+        dset = self._hdf[dataset][()]
+        attrs = self._hdf[dataset].attrs
+        first_dataset = "/" + dataset.split("/")[0] + "/"
+        timepoints = self._hdf[first_dataset].attrs["processed_timepoints"]
+
+        if "cell_label" in self._hdf[dataset].attrs:
+            ids = pd.MultiIndex.from_tuples(
+                zip(attrs["trap"], attrs["cell_label"]), names=["trap", "cell_label"]
+            )
+        else:
+            ids = pd.Index(attrs["trap"], names=["trap"])
+
+        return pd.DataFrame(dset, index=ids, columns=timepoints)
+
+    @staticmethod
+    def _if_ext_or_post(name):
+        if name.startswith("extraction") or name.startswith("postprocessing"):
+            if len(name.split("/")) > 3:
+                return name
+
+    @property
+    def datasets(self):
+        return signals._hdf.visit(self._if_ext_or_post)