'Load by delegating to sub-loaders.'

def load_adjusted_array(self, columns, dates, assets, mask):

    out = {}
    for col in columns:
        try:
            loader = self._loaders[col]
        except KeyError:
            raise ValueError(("Couldn't    find    loader    for    %s" % col))
        out.update(loader.load_adjusted_array([col], dates, assets, mask))
    return out
