added sort_signals to doc string of dump_file
@@ -214,6 +214,12 @@ def dump_file(database,
sort_signals=utils.DEFAULT):
"""Dump given database `database` to given file `filename`.
+ By default signals are sorted by their start bit in descending order
+ (unless you have passed `sort_signals = None` to load_file).
+ If you don't want them to be sorted pass `sort_signals = None`.
+ If you want the signals to be sorted in another way pass something like
+ `sort_signals = lambda signals: list(sorted(signals, key=lambda sig: sig.name))`
+
See :func:`~cantools.database.load_file()` for descriptions of
other arguments.
