Improve a couple of docstrings

beets/dbcore/db.py

@@ -734,7 +734,9 @@ class Database(object):
                 return conn
 
     def _close(self):
-        """Close the all connections to the underlying SQLite database.
+        """Close the all connections to the underlying SQLite database
+        from all threads. This does not render the database object
+        unusable; new connections can still be opened on demand.
         """
         thread_id = threading.current_thread().ident
         with self._shared_map_lock:

beetsplug/convert.py

@@ -219,6 +219,9 @@ class ConvertPlugin(BeetsPlugin):
 
     def convert_item(self, dest_dir, keep_new, path_formats, fmt,
                      pretend=False):
+        """A pipeline thread that converts `Item` objects from a
+        library.
+        """
         command, ext = get_format(fmt)
         item, original, converted = None, None, None
         while True: