Deform/Colander validator that has access to all nodes?

Question

How do you define a custom validator in Deform/Colander that has access to all node values. I need to access the values from two fields in order to decide if a particular value

Answer 1

Tangibly the answer is:

def verify_email_validator(form, values):
    if values['email_address'] != values['verify_email']:
        raise Invalid(form, 'Email values do not match')

class MySchema(MappingSchema):

    def __init__(self, *args, **kwargs):
        super(KickEntrySchema, self).__init__(*args, **kwargs)
        self.validator=verify_email_validator  # entire form validator

    email_address = SchemaNode(Email())
    verify_email = SchemaNode(Email())

Note the form validator is invoked only if none of the individual field validators raise an error.