docs: def validate_auth_mechanism_properties(option, value):
      """Validate authMechanismProperties."""
      value = validate_string(option, value)
      props = {}
      for opt in value.split(','):
          try:
              key, val = opt.split(':')
          except ValueError:
              raise ValueError("auth mechanism properties must be "
                               "key:value pairs like SERVICE_NAME:"
                               "mongodb, not %s." % (opt,))
          if key not in _MECHANISM_PROPS:
              raise ValueError("%s is not a supported auth "
                               "mechanism property. Must be one of "
                               "%s." % (key, tuple(_MECHANISM_PROPS)))
          if key == 'CANONICALIZE_HOST_NAME':
              props[key] = validate_boolean_or_string(key, val)
          else:
              props[key] = val
  
      return props