MongoDB_ycsb not recognizing os_type=Centos7

I am using trying to run YCSB with MongoDB on Centos 7.5 and I am seeing it is failing to recognize the attributes. Below is the error

Exception running benchmark
Traceback (most recent call last):
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/pkb.py", line 860, in RunBenchmarkTask
RunBenchmark(spec, collector)
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/pkb.py", line 711, in RunBenchmark
DoProvisionPhase(spec, detailed_timer)
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/pkb.py", line 515, in DoProvisionPhase
spec.ConstructVirtualMachines()
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/benchmark_spec.py", line 370, in ConstructVirtualMachines
vms = self.ConstructVirtualMachineGroup(group_name, group_spec)
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/benchmark_spec.py", line 289, in ConstructVirtualMachineGroup
static_vm_class = static_vm.GetStaticVmClass(vm_spec.os_type)
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/static_virtual_machine.py", line 294, in GetStaticVmClass
OS_TYPE=os_type)
File "/home/anupn/PerfKitBenchmarker/perfkitbenchmarker/resource.py", line 47, in GetResourceClass
(base_class.__name__, kwargs))
Exception: No BaseVirtualMachine subclass defined with the attributes: {'OS_TYPE': 'centos7', 'CLOUD': 'Static'}
2018-12-17 14:29:08,828 99e69746 MainThread mongodb_ycsb(1/1) ERROR Benchmark 1/1 mongodb_ycsb (UID: mongodb_ycsb0) failed. Execution will continue.

I am attaching my config file
[baremetal-static.txt](https://github.com/GoogleCloudPlatform/PerfKitBenchmarker/files/2688193/baremetal-static.txt)

Do I have to use os_type=rhel even for Centos7?