Rt::extension::import::csv Configuration isseu

I have the RT::extension::import::CSV working but having a problem with importing in the field “Held By”. Getting the error:
[warning]: Unknown asset field Held By for column Assigned User, skipping (/opt/rt/local/plugins/RT-Extension-Assets-Import-CSV/lib/RT/Extension/Assets/Import/CSV.pm:66)

Below is my configuration in the RT_SiteConfig.pm

Set( $AssetsImportUniqueCF, ‘Serial Number’ );
Set( %AssetsImportFieldMapping,
‘Name’ => ‘System Name’,
‘Catalog’ => ‘Neuro Hardware’,
‘Owner’ => ‘Neurology’,
‘Held By’ => ‘Assigned User’,
‘Contact’ => ‘NeurologyIT@URMC.Rochester.edu’,
‘CF.Manufacturer’ => ‘Make’,
‘CF.Model’ => ‘Model’,
‘CF.Neuro IT SN #’ => ‘Neuro IT Tag’,
‘CF.Serial Number’ => ‘Serial Number’,
‘CF.OS’ => ‘OS’,
‘CF.Location’ => ‘Location’,
‘CF.Division’ => ‘Division’,
‘CF.Asset Tag’ => ‘Asset Tag’,
‘CF.Notes’ => ‘Notes’,
Wondering how I can define the Held By name so it is recognized /rt-assets-import-csv?
B Barrett
University of Rochester Medical Center