Given the hash(namesapce_id, sender_script_pubkey, reveal_addr) for a 
        namespace that is being imported, get its associated NAMESPACE_PREORDER
        record.

        Return the namespace preorder record on success.
        Return None if not found, if the namespace is currently not preordered, or if the preorder record is expired.

def get_namespace_preorder( self, namespace_id_hash ):
        """
        Given the hash(namesapce_id, sender_script_pubkey, reveal_addr) for a 
        namespace that is being imported, get its associated NAMESPACE_PREORDER
        record.

        Return the namespace preorder record on success.
        Return None if not found, if the namespace is currently not preordered, or if the preorder record is expired.
        """
        namespace_preorder = namedb_get_namespace_preorder( self.db, namespace_id_hash, self.lastblock ) 
        return namespace_preorder