Start Client Enrollment.  Uses the POST to /enrollments interface.

        :Args:
            * *client*: (str) Client's Name
            * *mode*: (str) DEPRECATED. Presence of PIN is used to determine mode (AudioPass vs AudioPIN)
            * *pin*: (str) Client's PIN. 4 digit string
            * *phone_number*: (str) Phone number to call.

        :Returns: (dict) Enrollment record with prompts as described `here <https://cloud.knuverse.com/docs/api/#api-Enrollments-Start_enrollment>`_.

def enrollment_start(
            self,
            name,
            mode=None,
            pin=None,
            phone_number=None
    ):
        """
        Start Client Enrollment.  Uses the POST to /enrollments interface.

        :Args:
            * *client*: (str) Client's Name
            * *mode*: (str) DEPRECATED. Presence of PIN is used to determine mode (AudioPass vs AudioPIN)
            * *pin*: (str) Client's PIN. 4 digit string
            * *phone_number*: (str) Phone number to call.

        :Returns: (dict) Enrollment record with prompts as described `here <https://cloud.knuverse.com/docs/api/#api-Enrollments-Start_enrollment>`_.
        """
        data = {
            "name": name,
        }

        if mode:
            warning_msg = 'WARNING: The "mode" parameter for enrollment_start is DEPRECATED and will be ignored. ' \
                          'To avoid incompatibility with a future release please stop providing it.'
            print(warning_msg, file=sys.stderr)
        if pin:
            data["pin"] = pin
        if phone_number:
            data["phone_number"] = phone_number

        response = self._post(url.enrollments, body=data)
        self._check_response(response, 201)
        return self._create_response(response)