getObjectGraph with aggregate fields

$modx->getObjectGraph('Post', array(
            'Photos' => array(),
            'Comments' => array(
                'CreatedBy' => array()
            ),
            'CreatedBy' => array()
		), $id);

<object class="Post" table="post" extends="xPDOSimpleObject">
		<field key="name" dbtype="varchar" precision="255" phptype="string" null="false" default="" index="index" />
		<field key="description" dbtype="text" phptype="string" null="false" default="" />
		<field key="street1" dbtype="varchar" precision="255" phptype="string" null="false" default="" />
		<field key="street2" dbtype="varchar" precision="255" phptype="string" null="false" default="" />
		<field key="city" dbtype="varchar" precision="255" phptype="string" null="false" default="" />
		<field key="postcode" dbtype="varchar" precision="16" phptype="string" null="false" default="" />
		<field key="country" dbtype="varchar" precision="255" phptype="string" null="false" default="0" />
		<field key="logo" dbtype="varchar" precision="160" phptype="string" null="false" default="" />
		<field key="website" dbtype="varchar" precision="160" phptype="string" null="false" default="" />
		<field key="keywords" dbtype="varchar" precision="255" phptype="string" null="false" default="" />
		<field key="active" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" default="0" />

		<field key="createdon" dbtype="datetime" phptype="datetime" null="true" />
		<field key="createdby" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" default="0" index="index" />

		<index alias="name" name="name" primary="false" unique="false" type="BTREE">
			<column key="name" length="" collation="A" null="false" />
		</index>

		<index alias="createdby" name="createdby" primary="false" unique="false" type="BTREE">
			<column key="createdby" length="" collation="A" null="false" />
		</index>

		<aggregate alias="CreatedBy" class="modUser" local="createdby" foreign="id" cardinality="one" owner="foreign" />
		<composite alias="Comments" class="Comment" local="id" foreign="post" cardinality="many" owner="local" />
		<composite alias="Facilities" class="vxFacility" local="id" foreign="post" cardinality="many" owner="local" />
		<composite alias="Photos" class="vxPhoto" local="id" foreign="post" cardinality="many" owner="local" />
	</object>

	<object class="Comment" table="comments" extends="xPDOSimpleObject">
		<field key="post" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" default="0" index="index" />
		<field key="comments" dbtype="text" phptype="string" null="false" default="" />
		<field key="problems" dbtype="text" phptype="string" null="false" default="" />
		<field key="delegates" dbtype="varchar" precision="30" phptype="string" null="false" default="" />
		<field key="event_type" dbtype="varchar" precision="160" phptype="string" null="false" default="" />
		<field key="facilities" dbtype="text" phptype="json" null="false" default="{}" />
		<field key="ratings" dbtype="text" phptype="json" null="false" default="{}" />

		<field key="createdon" dbtype="datetime" phptype="datetime" null="true" />
		<field key="createdby" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" default="0" index="index" />

		<aggregate alias="CreatedBy" class="modUser" local="createdby" foreign="id" cardinality="one" owner="foreign" />
		<aggregate alias="Post" class="Post" local="post" foreign="id" cardinality="one" owner="foreign" />
	</object>