wpmem_export_fields

The array of export fields is keyed as 'meta_key' => 'heading value'.
The array will include all fields in the Fields tab, plus the following:

@type int    $ID               ID from wp_users
@type string $username         user_login from wp_users
@type string $user_nicename    user_nicename
@type string $user_url         user_url
@type string $display_name     display_name
@type int    $active           Whether the user is active/deactivated.
@type string $exp_type         If the PayPal extension is installed pending|subscrption (optional)
@type string $expires          If the PayPal extension is installed MM/DD/YYYY (optional)
@type string $user_registered  user_registered
@type string $user_ip          The IP of the user when they registered.
@type string $role             The user's role (or roles, if multiple).