alternateSymbols

The alternate symbols for the unique value's primary symbol. Symbols in this list should be of type MultilayerSymbol and must have SymbolReferenceProperties set with valid minimum and maximum scale at which symbol becomes visible. Renderer will pick only one symbol at a given map scale. If primary symbol's scale range falls within the map's scale, primary symbol is used. If not, then symbols in alternate symbols list are iterated through and first symbol matching the current map scale is picked for rendering. A symbol becomes visible if the map scale is less than or equal to symbol's minimum scale and greater than symbol's maximum scale.