'Called with a column of the result of a pipeline. This needs to put
the data into a format that can be used in a workspace to continue
doing computations.
Parameters
result : pd.Series
A multiindexed series with (dates, assets) whose values are the
results of running this pipeline term over the dates.
assets : pd.Index
All of the assets being requested. This allows us to correctly
shape the workspace value.
Returns
workspace_value : array-like
An array like value that the engine can consume.'

def to_workspace_value(self, result, assets):

    return result.unstack().fillna(self.missing_value).reindex(columns=assets, fill_value=self.missing_value).values
