code: def namedb_get_all_preordered_namespace_hashes( cur, current_block ):
      
      query = "SELECT preorder_hash FROM preorders WHERE op = ? AND block_number >= ? AND block_number < ?;"
      args = (NAMESPACE_PREORDER, current_block, current_block + NAMESPACE_PREORDER_EXPIRE )
  
      namespace_rows = namedb_query_execute( cur, query, args )
      ret = []
      for namespace_row in namespace_rows:
          ret.append( namespace_row['preorder_hash'] )
  
      return ret
docs: Get a list of all preordered namespace hashes that haven't expired yet.
      Used for testing