These credentials are requried for importing address tables from networks switches in import_switches_address_tables task in process of importers.tasks.import_all.
Sample /etc/racks/network-switches-credentials.yaml content:
<switch label>:
type: hp-procurve
username: username
password: password
<switch label>:
type: cisco-ios
username: username
password: password
Available type values are hp-procurve and cisco-ios. <switch label> is label for this switch in DCIM.