Given the *incoming* primitive data, return the value for this field
        that should be validated and transformed to a native value.

def get_value(self, dictionary):
        """
        Given the *incoming* primitive data, return the value for this field
        that should be validated and transformed to a native value.
        """
        if html.is_html_input(dictionary):
            # HTML forms will represent empty fields as '', and cannot
            # represent None or False values directly.
            if self.field_name not in dictionary:
                if getattr(self.root, 'partial', False):
                    return empty
                return self.default_empty_html
            ret = dictionary[self.field_name]
            if ret == '' and self.allow_null:
                # If the field is blank, and null is a valid value then
                # determine if we should use null instead.
                return '' if getattr(self, 'allow_blank', False) else None
            elif ret == '' and not self.required:
                # If the field is blank, and emptyness is valid then
                # determine if we should use emptyness instead.
                return '' if getattr(self, 'allow_blank', False) else empty
            return ret
        return dictionary.get(self.field_name, empty)