code: def create_db(self, instance_name, instance_type, admin_username,
              admin_password, security_groups=None, db_name=None,
              storage_size_gb=DEFAULT_STORAGE_SIZE_GB,
              timeout_s=DEFAULT_TIMEOUT_S):
          
          # TODO: investigate what upstream RedDwarf does for admin users
          return db_to_dict(
                  self._poll_instance_status(
                      self._create_db(instance_name, instance_type,
                          storage_size_gb),
                      timeout_s
                      )
                  )
docs: Creates a database instance.
  
          This method blocks until the db instance is active, or until
          :attr:`timeout_s` has elapsed.
  
          :param str instance_name:  A name to assign to the db instance.
  
          :param str instance_type:  The server instance type (e.g. ``medium``).
  
          :param str admin_username:  The admin username.
  
          :param str admin_password:  The admin password.
  
          :param security_groups:  A list of security groups in which to place
              the db instance.
          :type security_groups:  :class:`~collections.Iterable`
  
          :param str db_name:  The database name.  If this is not specified, the
              database will be named the same as the :attr:`instance_name`.
  
          :param int storage_size_gb:  The size of the storage volume in GB.
  
          :param float timeout_s:  The number of seconds to poll for an active
              database server before failing.
  
          :rtype:  :class:`dict`