@abc.abstractmethod<EOL><INDENT>def get_commitments_by_query(self, commitment_query):<DEDENT>
return<EOL>
Gets a list of ``Commitments`` matching the given commitment query.

        :param commitment_query: the commitment query
        :type commitment_query: ``osid.calendaring.CommitmentQuery``
        :return: the returned ``CommitmentList``
        :rtype: ``osid.calendaring.CommitmentList``
        :raise: ``NullArgument`` -- ``commitment_query is null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure
        :raise: ``Unsupported`` -- ``commitment_query`` is not of this service

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