public Cluster field(Object field) {
if (field instanceof String) {
this.selectedFields.put((String) field, this.fields.get(field));
} else if (field instanceof CalcMultiField) {
CalcMultiField multiField = (CalcMultiField) field;
multiField.config(this);
this.fields.put(multiField.getName(), multiField);
this.selectedFields.put(multiField.getName(), multiField);
}
return this;
}