set subgrids(subgridSpecs) {
        var subgrids = this._subgrids = [];

        subgrids.lookup = {};

        subgridSpecs.forEach(function(spec) {
            if (spec) {
                subgrids.push(this.createSubgrid(spec));
            }
        }, this);

        this.shapeChanged();
    }
An array where each element represents a subgrid to be rendered in the hypergrid.

The list should always include at least one "data" subgrid, typically {@link Behavior#dataModel|dataModel}.
It may also include zero or more other types of subgrids such as header, filter, and summary subgrids.

This object also sports a dictionary of subgrids in `lookup` property where each dictionary key is one of:
* **`subgrid.name`** (for those that have a defined name, which is presumed to be unique)
* **`subgrid.type`** (not unique, so if you plan on having multiple, name them!)
* **`'data'`** for the (one and only) data subgrid when unnamed (note that data subgrids have no `type`)

The setter:
* "Enlivens" any constructors (see {@link Behavior~createSubgrid|createSubgrid} for details).
* Reconstructs the dictionary.
* Calls {@link Behavior#shapeChanged|shapeChanged()}.

@param {subgridSpec[]} subgridSpecs

@type {DataModel[]}

@memberOf Behavior#