Macro define_multi_property

macro_rules! define_multi_property {
    (
        $person_property:ident,
        ( $($dependency:ident),+ )
    ) => { ... };
}

Defines a named multi-property composed of a tuple of several existing other properties.

• $person_property: The name of the new multi-property type.
• ( $($dependency),+ ): A non-empty, comma-separated, ordered list of existing
  property identifiers that this multi-property is composed from.