List companies for which the client has ACL visibility.
.. attribute:: parent
Required. Resource name of the tenant under which the company
is created. The format is
"projects/{project_id}/tenants/{tenant_id}", for example,
"projects/foo/tenant/bar". If tenant id is unspecified, the
default tenant will be used, for example, "projects/foo".
The maximum number of companies to be returned, at most 100.
Default is 100 if a non-positive number is provided.
