I want to add some data in metafields. I use this code but this is not working

[KomalDeveloper01]

$GetAgentId ="789459879696"; $data = array('key' => 'agent_customers','value'=>'abc','type' =>'multi_line_text_field','namespace' =>'custom'); $Customer = $shopify->Customer($GetAgentId)->Metafield()->put($data);