'Returns
adjustments : list[dict[int -> Adjustment]]
A list, where each element corresponds to the `columns`, of
mappings from index to adjustment objects to apply at that index.'

def load_adjustments(self, columns, dts, assets):

    out = ([None] * len(columns))
    for (i, column) in enumerate(columns):
        adjs = {}
        for asset in assets:
            adjs.update(self._get_adjustments_in_range(asset, dts, column))
        out[i] = adjs
    return out
