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.entity.AttributeModifier;

ZenGetter	GetterMethod	戻り値
ZenGetter uuid	GetterMethod getUUID()	戻り値 string
ZenGetter name	GetterMethod getName()	戻り値 string
ZenGetter operation	GetterMethod getOperation()	戻り値 int
ZenGetter amount	GetterMethod getAmount()	戻り値 double
ZenGetter saved	GetterMethod isSaved()	戻り値 boolean型

SetterName	SetterMethod	Parameter Type
SetterName saved	SetterMethod setSaved(boolean)	Parameter Type boolean型

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for operation:
0 = add: Increment X by Amount
1 = multiply_base: Increment Y by X * Amount
2 = multiply: Y = Y * (1 + Amount) (equivalent to Increment Y by Y * Amount).

ZenScript
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AttributeModifier.createModifier(String name, double amount, int operation, @Optional String uuid);