def get_feature_variable_double(self, feature_key, variable_key, user_id, attributes=None):
    """ Returns value for a certain double variable attached to a feature flag.

    Args:
      feature_key: Key of the feature whose variable's value is being accessed.
      variable_key: Key of the variable whose value is to be accessed.
      user_id: ID for user.
      attributes: Dict representing user attributes.

    Returns:
      Double value of the variable. None if:
      - Feature key is invalid.
      - Variable key is invalid.
      - Mismatch with type of variable.
    """

    variable_type = entities.Variable.Type.DOUBLE
    return self._get_feature_variable_for_type(feature_key, variable_key, variable_type, user_id, attributes)
Returns value for a certain double variable attached to a feature flag.

    Args:
      feature_key: Key of the feature whose variable's value is being accessed.
      variable_key: Key of the variable whose value is to be accessed.
      user_id: ID for user.
      attributes: Dict representing user attributes.

    Returns:
      Double value of the variable. None if:
      - Feature key is invalid.
      - Variable key is invalid.
      - Mismatch with type of variable.