interface ContentEntityTypeInterface

interface ContentEntityTypeInterface extends EntityTypeInterface {
    
    /**
     * Gets an array of entity revision metadata keys.
     *
     * @return array
     *   An array describing how the Field API can extract revision metadata
     *   information of this entity type:
     *   - revision_log_message: The name of the property that contains description
     *     of the changes that were made in the current revision.
     *   - revision_user: The name of the property that contains the user ID of
     *     the author of the current revision.
     *   - revision_created: The name of the property that contains the timestamp
     *     of the current revision.
     */
    public function getRevisionMetadataKeys();
    
    /**
     * Gets a specific entity revision metadata key.
     *
     * @param string $key
     *   The name of the entity revision metadata key to return.
     *
     * @return string|bool
     *   The entity revision metadata key, or FALSE if it does not exist.
     *
     * @see self::getRevisionMetadataKeys()
     */
    public function getRevisionMetadataKey($key);
    
    /**
     * Indicates if a given entity revision metadata key exists.
     *
     * @param string $key
     *   The name of the entity revision metadata key to check.
     *
     * @return bool
     *   TRUE if a given entity revision metadata key exists, FALSE otherwise.
     */
    public function hasRevisionMetadataKey($key);
    
    /**
     * Sets a revision metadata key.
     *
     * @param string $key
     *   The name of the entity revision metadata key to set.
     * @param string|null $field_name
     *   The name of the entity field key to use for the revision metadata key. If
     *   NULL is passed, the value of the revision metadata key is unset.
     *
     * @return $this
     */
    public function setRevisionMetadataKey($key, $field_name);

}