def get_fieldsets_attr(sets, cache_attr='_fieldsets'):
    """
    Get a form attribute for getting groups of (bound) fields.

        class MyForm(forms.Form):
            first_name = forms.Charfield()
            last_name = forms.Charfield()
            email = forms.Charfield()
            phone = forms.Charfield()
            
            SETS = {'name_fields': ('first_name', 'last_name'),
                    'contact_fields': ('email', 'phone')}
            fieldsets = get_fieldsets_attr(sets=SETS)

    This is specially usefull in templates:

        <form method="POST" action="">
          <fieldset>
            <legend>Name</legend>
            {% for field in form.fieldsets.name_fields %}
              {% include "includes/form_field.html" %}
            {% endfor %}
          </fieldset>

          <fieldset>
            <legend>Contact</legend>
            {% for field in form.fieldsets.contact_fields %}
              {% include "includes/form_field.html" %}
            {% endfor %}
          </fieldset>
        </form>
    """
    def inner(self):
        if not hasattr(self, cache_attr):
            from django.forms.forms import BoundField
            fieldsets = {}
            for key, fieldnames in sets.items():
                fieldsets[key] = []
                for fieldname in fieldnames:
                    fieldsets[key].append(BoundField(self, self.fields[fieldname], fieldname))
            self.cache_attr = fieldsets
        return self.cache_attr
    return inner