Here is the problem I am facing:
1. I use the autotest UI, and in advanced options, I can put in test args.
I put in my test args as follows:
args=test:power_Dummy

2. This gets injected to the control file, which looks like the following:
# INJECT_BEGIN - DO NOT DELETE THIS LINE
args='test:power_Dummy'
args_dict={'args': 'test:power_Dummy'}
# INJECT_END - DO NOT DELETE LINE
# INJECT_BEGIN - DO NOT DELETE THIS LINE
test='power_Dummy'
args_dict={'test': 'power_Dummy'}
# INJECT_END - DO NOT DELETE LINE
def step_init():
    step0()

def step0():
    # Copyright 2018 The Chromium OS Authors. All rights reserved.
    # Use of this source code is governed by a BSD-style license that can be
    # found in the LICENSE file.
    
    from autotest_lib.server import utils
    
    AUTHOR = "Chrome OS Team"
    NAME = "power_ServoV4ChargeWrapper"
    PURPOSE = "Use Servo v4 to control charging / discharging the DUT"
    CRITERIA = ""
    TIME = "LONG"
    TEST_CATEGORY = "Functional"
    TEST_CLASS = "power"
    TEST_TYPE = "server"
    DEPENDENCIES = "servo"
    
    DOC = """
DUT is connected to Servo v4 via USB type-C, and Servo v4 is connected to AC
power.

Sample usage:
test_that <ip address of DUT> power_ServoV4ChargeWrapper \
--args 'servo_host=localhost servo_port=9999 test=power_Dummy'

What are the parameters:
test: the client test to run in wrapper test; required.
servo_host: host of servod instance; required.
servo_port: port that the servod instance is on; required.
"""
    
    args_dict = utils.args_to_dict(args)
    servo_args = hosts.CrosHost.get_servo_arguments(args_dict)
    
    def run(machine):
        host = hosts.create_host(machine, servo_args=servo_args)
        job.run_test("power_ServoV4ChargeWrapper", host=host, config=args_dict)
    
    parallel_simple(run, machines)

step_init()

3. I expect this to wrok, but instead, I get the following error:
Traceback (most recent call last):
  File "/usr/local/autotest/client/common_lib/test.py", line 600, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 800, in _call_test_function
    return func(*args, **dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 464, in execute
    postprocess_profiled_run, args, dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 371, in _call_run_once
    self.run_once(*args, **dargs)
  File "/usr/local/autotest/server/site_tests/power_ServoV4ChargeWrapper/power_ServoV4ChargeWrapper.py", line 31, in run_once
    raise error.TestNAError(msg)
TestNAError: power_ServoV4ChargeWrapper must run with args input.