Create a new DBInstance Read Replica.

        :type id: str
        :param id: Unique identifier for the new instance.
                   Must contain 1-63 alphanumeric characters.
                   First character must be a letter.
                   May not end with a hyphen or contain two consecutive hyphens

        :type source_id: str
        :param source_id: Unique identifier for the DB Instance for which this
                          DB Instance will act as a Read Replica.

        :type instance_class: str
        :param instance_class: The compute and memory capacity of the
                               DBInstance.  Default is to inherit from
                               the source DB Instance.

                               Valid values are:

                               * db.m1.small
                               * db.m1.large
                               * db.m1.xlarge
                               * db.m2.xlarge
                               * db.m2.2xlarge
                               * db.m2.4xlarge

        :type port: int
        :param port: Port number on which database accepts connections.
                     Default is to inherit from source DB Instance.
                     Valid values [1115-65535].  Defaults to 3306.

        :type availability_zone: str
        :param availability_zone: Name of the availability zone to place
                                  DBInstance into.

        :type auto_minor_version_upgrade: bool
        :param auto_minor_version_upgrade: Indicates that minor engine
                                           upgrades will be applied
                                           automatically to the Read Replica
                                           during the maintenance window.
                                           Default is to inherit this value
                                           from the source DB Instance.

        :rtype: :class:`boto.rds.dbinstance.DBInstance`
        :return: The new db instance.

def create_dbinstance_read_replica(self, id, source_id,
                                       instance_class=None,
                                       port=3306,
                                       availability_zone=None,
                                       auto_minor_version_upgrade=None):
        """
        Create a new DBInstance Read Replica.

        :type id: str
        :param id: Unique identifier for the new instance.
                   Must contain 1-63 alphanumeric characters.
                   First character must be a letter.
                   May not end with a hyphen or contain two consecutive hyphens

        :type source_id: str
        :param source_id: Unique identifier for the DB Instance for which this
                          DB Instance will act as a Read Replica.

        :type instance_class: str
        :param instance_class: The compute and memory capacity of the
                               DBInstance.  Default is to inherit from
                               the source DB Instance.

                               Valid values are:

                               * db.m1.small
                               * db.m1.large
                               * db.m1.xlarge
                               * db.m2.xlarge
                               * db.m2.2xlarge
                               * db.m2.4xlarge

        :type port: int
        :param port: Port number on which database accepts connections.
                     Default is to inherit from source DB Instance.
                     Valid values [1115-65535].  Defaults to 3306.

        :type availability_zone: str
        :param availability_zone: Name of the availability zone to place
                                  DBInstance into.

        :type auto_minor_version_upgrade: bool
        :param auto_minor_version_upgrade: Indicates that minor engine
                                           upgrades will be applied
                                           automatically to the Read Replica
                                           during the maintenance window.
                                           Default is to inherit this value
                                           from the source DB Instance.

        :rtype: :class:`boto.rds.dbinstance.DBInstance`
        :return: The new db instance.
        """
        params = {'DBInstanceIdentifier' : id,
                  'SourceDBInstanceIdentifier' : source_id}
        if instance_class:
            params['DBInstanceClass'] = instance_class
        if port:
            params['Port'] = port
        if availability_zone:
            params['AvailabilityZone'] = availability_zone
        if auto_minor_version_upgrade is not None:
            if auto_minor_version_upgrade is True:
                params['AutoMinorVersionUpgrade'] = 'true'
            else:
                params['AutoMinorVersionUpgrade'] = 'false'

        return self.get_object('CreateDBInstanceReadReplica',
                               params, DBInstance)