@abc.abstractmethod<EOL><INDENT>def is_in_circle(self, agent_id):<DEDENT>
return<EOL>
Tests if the given agent is inside the given circle of trust.

        :param agent_id: an agent ``Id``
        :type agent_id: ``osid.id.Id``
        :return: ``true`` if the agent is in the given trust, ``false`` if agent not found or is outside the circle
        :rtype: ``boolean``
        :raise: ``NullArgument`` -- ``agent_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*