Try fix issue #323

- modify some functions decorated with path_or_mth5 so that
they operate in read-only mode, so that the channel summary is not
recomputed when the file is closed

aurora/pipelines/fourier_coefficients.py

@@ -234,7 +234,7 @@ def add_fcs_to_mth5(m, fc_decimations=None):
 
 
 @path_or_mth5_object
-def read_back_fcs(m):
+def read_back_fcs(m, mode="r"):
     """
     This is mostly a helper function for tests.  It was used as a sanity check while debugging the FC files, and
     also is a good example for how to access the data at each level for each channel.

aurora/pipelines/transfer_function_kernel.py

@@ -212,7 +212,13 @@ def check_if_fcs_already_exist(self):
             remote = run_sub_df.remote.iloc[0]
             mth5_path = run_sub_df.mth5_path.iloc[0]
             fcs_present = mth5_has_fcs(
-                mth5_path, survey_id, station_id, run_id, remote, self.processing_config
+                mth5_path,
+                survey_id,
+                station_id,
+                run_id,
+                remote,
+                self.processing_config,
+                mode="r",
             )
             self.dataset_df.loc[dataset_df_indices, "fc"] = fcs_present
 
@@ -618,14 +624,16 @@ def memory_warning(self):
 
 
 @path_or_mth5_object
-def mth5_has_fcs(m, survey_id, station_id, run_id, remote, processing_config):
+def mth5_has_fcs(m, survey_id, station_id, run_id, remote, processing_config, **kwargs):
     """
     Checks if all needed fc-levels for survey-station-run are present under processing_config
 
     Note #1: At this point in the logic, it is established that there are FCs associated with run_id and there are
         at least as many FC decimation levels as we require as per the processing config.  The next step is to
         assert whether it is True that the existing FCs conform to the recipe in the processing config.
 
+    kwargs are here as a pass through to the decorator ... we pass mode="r","a","w"
+
     Parameters
     ----------
     m