HTML+Flask form field

FLASK-WTFromds file:

class NonValidatingSelectField(SelectField):
    def pre_validate(self, form):
        pass

    device_model = NonValidatingSelectField('MODEL', validators=[Optional()], choices=[('0','No selection')]+[])

######################################################
HTML file

<div class="card-block edit wrapper">
                        <div class="form-group input-form-group">
                            {% for line in form.devices %}
                            {{ line.hidden_tag() }}
                            <div class="row">
                                <div class="col">
                                    {{ line.device_type.label}}
                                    {{ line.device_type(class='form-control custom-select device-type') }}
                                    {% for error in line.device_type.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col">
                                    {{ line.device_subtype.label }}
                                    {% if line.device_type.data == 'Misc' %}
                                    {{ line.device_subtype(class='form-control custom-select device-subtype') }}
                                    {% else %}
                                    {{ line.device_subtype(class='form-control custom-select device-subtype', disabled=true) }}
                                    {% endif %}
                                    {% for error in line.device_subtype.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col-3">
                                    {{ line.device_model.label}}
                                    {% if line.device_type.data == 'Software' %}
                                    {{ line.device_model(class='form-control device-model', disabled=true) }}
                                    {% else %}
                                    {{ line.device_model(class='form-control device-model') }}
                                    {% endif %}
                                    {% for error in line.device_model.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col-1">
                                    {{ line.device_count.label}}
                                    {{ line.device_count(class='form-control device-count') }}
                                    {% for error in line.device_count.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col">
                                    {{ line.device_label.label}}
                                    {% if line.device_type.data == 'Misc' or  line.device_type.data == 'Software' %}
                                    {{ line.device_label(class='form-control device-label', disabled=true) }}
                                    {% else %}
                                    {{ line.device_label(class='form-control device-label', required=true) }}
                                    {% endif %}
                                    <small class="form-text text-muted device-label-help"></small>
                                    {% for error in line.device_label.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col">
                                    {{ line.device_comment.label}}
                                    {% if line.device_type.data == 'Software' %}
                                    {{ line.device_comment(class='form-control device-comment', required=true) }}
                                    {% else %}
                                    {{ line.device_comment(class='form-control device-comment') }}
                                    {% endif %}
                                    {% for error in line.device_comment.errors %}
                                    <p class="form-control-status text-danger">
                                        {{ error }}
                                    </p>
                                    {% endfor %}
                                </div>
                                <div class="col">
                                    <label>&nbsp;</label>
                                    {{ line.delete_line(class='btn btn-danger pull-xs-left') }}
                                </div>
                            </div>
                            {% endfor %}
                        </div>
                    </div>