public function setEmployees(
        array $employees)
    {
        $this->_employees = $employees;

        // We now need to construct a new, inner value for the property. Since
        // it's a "mixed" property, it only accepts basic PHP types.
        $newInnerValue = [];
        foreach ($this->_employees as $k => $v) {
            $newInnerValue[$k] = is_object($v) && $v instanceof LazyJsonMapper
                               ? $v->asArray() // Throws.
                               : $v; // Is already a valid value.
        }

        // Now use the internal _setProperty() API to set the new inner value.
        // NOTE: This function only throws if the new value contains any
        // invalid non-basic data. Only basic PHP types are accepted.
        $this->_setProperty('employees', $newInnerValue);

        return $this;
    }