In python module troposphere I am getting an error "AttributeError: 'module' object has no attribute 'EBSBlockDeviceMapping'"

I'm following the example of some other code that has been written. The code in question looks like this:

   if virtualname == "ebs":
        if deviceSize == None:
            deviceSize = 8

            if delOnTerminate == None or delOnTerminate == "true":
                DOT = "true"
            else:
                DOT = "false"

        lc.BlockDeviceMappings.append(ec2.EBSBlockDeviceMapping(
                                            DeviceName=blockname,
                                            Ebs=ec2.EBSBlockDevice(VolumeSize=deviceSize,
                                                                   DeleteOnTermination=DOT)))
    else:
        lc.BlockDeviceMappings.append(ec2.BlockDeviceMapping(DeviceName=blockname,
                                                             VirtualName=virtualname))