def addField(self, field):
        """
        Add a field to this form.

        Fields are added in order, and C{fields} is a dictionary of the
        named fields, that is kept in sync only if this method is used for
        adding new fields. Multiple fields with the same name are disallowed.
        """
        if field.var is not None:
            if self.fields in field.var:
                raise Error("Duplicate field %r" % field.var)

            self.fields[field.var] = field

        self.fieldList.append(field)
dataset/ETHPy150Open ralphm/wokkel/wokkel/data_form.py/Form.addField/swapped operands of `in`