The write_data methods invokes the relevant AssetDBWriter subclass
to write data to the database. update_asset_finder is no longer
a relevant method since the AssetFinder is strictly a reader class.
This makes the drift and standard deviation used in RandomWalkSource
keyword args to give the user more control over the price series that
are emitted.
The standard deviation of prices is very different at different frequencies,
users should have the ability to specify the standard deviation used.
The drift term should also be configurable to give the user more control.
This adds a new data source that emits events
with certain user-specified frequency (minute
or daily).
This allows users to backtest and debug an
algorithm in minute mode to provide a cleaner
path towards Quantopian.
Stewart Douglas