code: def get_db_from_db(db_string):
      
      server = get_server_from_db(db_string)
      local_match = PLAIN_RE.match(db_string)
      remote_match = URL_RE.match(db_string)
      # If this looks like a local specifier:
      if local_match:
          return server[local_match.groupdict()['database']]
      elif remote_match:
          return server[remote_match.groupdict()['database']]
      raise ValueError('Invalid database string: %r' % (db_string,))
docs: Return a CouchDB database instance from a database string.