Example of acquiring the namepace from a collection object in Islandora

collection.php

<?php

// Load the collection object.
$object = islandora_object_load('the:pid');

// Instantiate a CollectionPolicy object with our policy. 
$collection_policy = new CollectionPolicy($object['COLLECTION_POLICY']->content);

// Grab the models.
$models = $collection_policy->getContentModels();

// Grab the desired namespace.
// For sanity, may want to pass this through islandora_get_namespace(), as we've not always
// written only the namespace itself... Occasionally, it may look like a full PID.:
// @see https://github.com/Islandora/islandora/blob/fd95c8dce72a8c6fbb7e36021b448781a3055909/includes/utilities.inc#L256-L276
$namespace = $models['the:relevantCModel']['namespace'];