adding docstring in test sleep readers, error handling for missing ac…

…tigraphy files in sleep readers

src/sleepecg/io/sleep_readers.py

@@ -8,6 +8,7 @@
 
 import csv
 import datetime
+import os
 from collections.abc import Iterator
 from dataclasses import dataclass
 from enum import IntEnum
@@ -444,6 +445,9 @@ def read_mesa(
 
                 activity_data = []
 
+                if not os.path.exists(activity_filepath):
+                    print(f"Skipping {record_id} due to missing activity data.")
+
                 with open(activity_filepath) as csv_file:
                     reader = csv.reader(csv_file, delimiter=",")
                     header = next(reader)

tests/test_sleep_readers.py

@@ -25,6 +25,7 @@ def _dummy_nsrr_overlap(filename: str, mesa_ids: list[int]):
 
 
 def _dummy_nsrr_actigraphy(filename: str, mesa_id: str):
+    """Create dummy actigraphy file with four usable activity counts."""
     base_time = datetime.datetime(2024, 1, 1, 20, 30, 0)
 
     linetimes = [
@@ -39,6 +40,7 @@ def _dummy_nsrr_actigraphy(filename: str, mesa_id: str):
 
 
 def _dummy_nsrr_actigraphy_cached(filename: str):
+    """Create dummy npy file that resembles cached activity counts."""
     activity_counts = np.array([10, 10, 10, 10, 10, 10])
     np.save(filename, activity_counts)