yank: error in running the included examples

I have the following error if i run any of the included examples, any advice? Thanks Omar

(base) om@om-SYS-4028GR-TR:~/yank-examples/examples/binding/t4-lysozyme$ yank selftest


YANK Selftest
-------------
Yank Version 0.25.2 

Available OpenMM platforms:
    0 Reference
    1 CPU
    2 CUDA
    3 OpenCL



Valid OpenEye install not found
Not required, but please check install if you expected it


Checking GPU Computed Mode (if present)...
Found 6 NVIDIA GPUs in the following modes: [Default, Default, Default, Default, Default, Default]
These should all be in shared/Default mode for YANK to use them
YANK Selftest complete.
Thank you for using YANK!

(base) om@om-SYS-4028GR-TR:~/yank-examples/examples/binding/t4-lysozyme$ sh run-all-ligands-explicit.sh 
Running simulation...
found unknown parameter number_of_iterations
Traceback (most recent call last):
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/experiment.py", line 1191, in _validate_options
    special_conversions=special_conversions)
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/utils.py", line 1058, in validate_parameters
    raise TypeError("found unknown parameter {}".format(', '.join(diff)))
TypeError: found unknown parameter number_of_iterations

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/om/anaconda3/bin/yank", line 11, in <module>
    load_entry_point('yank==0.25.2', 'console_scripts', 'yank')()
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/cli.py", line 73, in main
    dispatched = getattr(commands, command).dispatch(command_args)
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/commands/script.py", line 147, in dispatch
    yaml_builder = ExperimentBuilder(script=yaml_path, job_id=job_id, n_jobs=n_jobs)
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/experiment.py", line 591, in __init__
    self.parse(script)
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/experiment.py", line 681, in parse
    validate_general_options=True))
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/experiment.py", line 1193, in _validate_options
    raise YamlParseError(str(e))
yank.experiment.YamlParseError: found unknown parameter number_of_iterations
Analyzing data...
Traceback (most recent call last):
  File "/home/om/anaconda3/bin/yank", line 11, in <module>
    load_entry_point('yank==0.25.2', 'console_scripts', 'yank')()
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/cli.py", line 73, in main
    dispatched = getattr(commands, command).dispatch(command_args)
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/commands/analyze.py", line 107, in dispatch
    from .. import utils, analyze
  File "/home/om/anaconda3/lib/python3.7/site-packages/yank-0.25.2-py3.7.egg/yank/analyze.py", line 49, in <module>
    yank_registry = mmtools.multistate.default_observables_registry
AttributeError: module 'openmmtools' has no attribute 'multistate'
(base) om@om-SYS-4028GR-TR:~/yank-examples/examples/binding/t4-lysozyme$