diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigDependencyManager.php b/core/lib/Drupal/Core/Config/Entity/ConfigDependencyManager.php
index fc76841..8f7eb1b 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigDependencyManager.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigDependencyManager.php
@@ -11,7 +11,40 @@
 use Drupal\Component\Utility\SortArray;
 
 /**
- * Class ConfigDependencyManager
+ * Provides a class to discover configuration entity dependencies.
+ *
+ * Configuration entities can depend on modules, themes and other configuration
+ * entities. The dependency system is used during configuration installation to
+ * ensure that configuration entities are imported in the correct order. For
+ * example, node types are created before their fields and the fields are
+ * created before their field instances.
+ *
+ * Dependencies are written to the configuration entity so that they can be
+ * checked without the module that provides the configuration entity class being
+ * installed. This is important for configuration synchronization which needs to
+ * be able to validate configuration in the staging directory before the
+ * synchronization has occurred.
+ *
+ * Configuration entities determine their dependencies by implementing
+ * \Drupal\Core\Config\Entity\ConfigEntityInterface::calculateDependencies().
+ * This method should be called from the entity's implementation of
+ * \Drupal\Core\Entity\EntityInterface::preSave(). Implementations should use
+ * the helper method
+ * \Drupal\Core\Config\Entity\ConfigEntityBase::addDependency() to add
+ * dependencies. All the implementations in core call the parent method
+ * \Drupal\Core\Config\Entity\ConfigEntityBase::calculateDependencies() which
+ * resets the dependencies and provides an implementation to determine the
+ * plugin providers for configuration entities that implement
+ * \Drupal\Core\Config\Entity\EntityWithPluginBagInterface.
+ *
+ * The configuration manager service provides methods to find dependencies for
+ * a specified module, theme or configuration entity.
+ *
+ * @see \Drupal\Core\Config\Entity\ConfigEntityInterface::calculateDependencies()
+ * @see \Drupal\Core\Config\Entity\ConfigEntityInterface::getConfigDependencyName()
+ * @see \Drupal\Core\Config\Entity\ConfigEntityBase::addDependency()
+ * @see \Drupal\Core\Config\ConfigInstaller::installDefaultConfig()
+ * @see \Drupal\Core\Config\Entity\ConfigEntityDependency
  */
 class ConfigDependencyManager {
 
@@ -168,6 +201,7 @@ public function setData(array $data) {
       $config = new ConfigEntityDependency($name, $config);
     });
     $this->data = $data;
+    $this->graph = NULL;
     return $this;
   }