It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.text.IStyle;

ZenGetter	ZenSetter	Type
ZenGetter parent	ZenSetter parent	Type IStyle
ZenGetter bold	ZenSetter bold	Type bool
ZenGetter italic	ZenSetter italic	Type bool
ZenGetter underline	ZenSetter underline	Type bool
ZenGetter strikethrough	ZenSetter strikethrough	Type bool
ZenGetter obfuscated	ZenSetter obfuscated	Type bool
ZenGetter umieszczenie	ZenSetter umieszczenie	Type bool
ZenGetter color	ZenSetter color	Type string

• IStyle createShallowCopy();

Creates a shallow copy of this style. Changes to this instance's values will not be reflected in the copy, but changes to the parent style's values WILL be reflected in both this instance and the copy, wherever either does not override a value.

• IStyle createDeepCopy();

Creates a deep copy of this style. No changes to this instance or its parent style will be reflected in the copy.