def clean(self, value):
        """
        Validates every value in the given list. A value is validated against
        the corresponding Field in self.fields.

        For example, if this MultiValueField was instantiated with
        fields=(DateField(), TimeField()), clean() would call
        DateField.clean(value[0]) and TimeField.clean(value[1]).
        """
        clean_data = []
        errors = []
        if not value or isinstance(value, (list, tuple)):
            if not value or not [v for v in value if self.empty_values not in v]:
                if self.required:
                    raise ValidationError(self.error_messages['required'], code='required')
                else:
                    return self.compress([])
        else:
            raise ValidationError(self.error_messages['invalid'], code='invalid')
        for i, field in enumerate(self.fields):
            try:
                field_value = value[i]
            except IndexError:
                field_value = None
            if field_value in self.empty_values:
                if self.require_all_fields:
                    # Raise a 'required' error if the MultiValueField is
                    # required and any field is empty.
                    if self.required:
                        raise ValidationError(self.error_messages['required'], code='required')
                elif field.required:
                    # Otherwise, add an 'incomplete' error to the list of
                    # collected errors and skip field cleaning, if a required
                    # field is empty.
                    if field.error_messages['incomplete'] not in errors:
                        errors.append(field.error_messages['incomplete'])
                    continue
            try:
                clean_data.append(field.clean(field_value))
            except ValidationError as e:
                # Collect all validation errors in a single list, which we'll
                # raise at the end of clean(), rather than raising a single
                # exception for the first error we encounter. Skip duplicates.
                errors.extend(m for m in e.error_list if m not in errors)
        if errors:
            raise ValidationError(errors)

        out = self.compress(clean_data)
        self.validate(out)
        self.run_validators(out)
        return out
dataset/ETHPy150Open django/django/django/forms/fields.py/MultiValueField.clean/swapped operands of `not in`