How to translate forms using trans? {% trans '' %}

Hi, I translate all static content with no problem. But how can I translate the forms that are shown in the template?
In template I use: {% trans ‘Example’ %}
How can I use ‘trans’ in forms?


class LoginForm(forms.ModelForm):
    username = forms.CharField(label='User')
    password = forms.CharField(label='Password')

    class Meta:
        model = User
        fields = ('username', 'password')

    def __init__(self,*args, **kwargs):
        super(LoginForm, self).__init__(*args, **kwargs)
        self.fields['username'].widget.attrs.update({'class': 'form-control'})
        self.fields['username'].label = "User"
        self.fields['password'].widget.attrs.update({'class': 'form-control','type':'password'})
        self.fields['password'].label = "Password"

ugettext = lambda s: s 
    ('EN',    '{}'.format(ugettext('EN'))),
    ('ES',    '{}'.format(ugettext('ES'))),
    ('EU',    '{}'.format(ugettext('EU'))),
    ('FR',    '{}'.format(ugettext('FR'))),

TIME_ZONE = 'Europe/Madrid'
USE_I18N = True
USE_L10N = True
USE_TZ = True
    os.path.join(BASE_DIR, "locale"),

Looks like you really need to read Translation | Django documentation | Django !!