{% for field in form.visible_fields %}
  <li class="{{ field.name|slugify }}{% if field.css_classes %} {{ field.css_classes }}{% endif %}">
    {{ field.label_tag }}
    <div class="field">{{ field }}</div>
    {% if field.help_text %}<span class="helptext">{{ field.help_text }}</span>{% endif %}
    {{ field.errors }}
  </li>
{% endfor %}

{% for field in form.visible_fields %}
  <li class="{{ field.name|slugify }}{% if field.css_classes %} {{ field.css_classes }}{% endif %}{% if field.field.widget.input_type %} type-{{ field.field.widget.input_type }}{% endif %}">
    {{ field.label_tag }}
    <div class="field">{{ field }}</div>
    {% if field.help_text %}<span class="helptext">{{ field.help_text }}</span>{% endif %}
    {{ field.errors }}
  </li>
{% endfor %}

Add class to field li wrapper with input type if available.
Add class to field li wrapper with input type if available.