<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_params(self, validator_parameter, name_prefix):
 """Retrieves additional user-supplied params for the job and validates them. Args: validator_parameter: name of the request parameter which supplies validator for this parameter set. name_prefix: common prefix for all parameter names in the request. Raises: Any exception raised by the 'params_validator' request parameter if the params fail to validate. Returns: The user parameters. """

    params_validator = self.request.get(validator_parameter)

    user_params = {}
    for key in self.request.arguments():
      if key.startswith(name_prefix):
        values = self.request.get_all(key)
        adjusted_key = key[len(name_prefix):]
        if len(values) == 1:
          user_params[adjusted_key] = values[0]
        else:
          user_params[adjusted_key] = values

    if params_validator:
      resolved_validator = util.for_name(params_validator)
      resolved_validator(user_params)

    return user_params