Add documentation

sohstationviewer/model/mseed_data/mseed.py

@@ -37,6 +37,8 @@ class MSeed(GeneralData):
             f"WHERE dataType='{self.data_type}'"
         )
         channels_db_info = execute_db_dict(channels_sql)
+        # dict containing some additional information about each channel. An
+        # example is whether to read all data points from a channel.
         self.channels_db_info = {
             channel_info['channel']: int(channel_info['readAllPoints'])
             for channel_info in channels_db_info