public boolean isAssignableFrom(DataType dataType) {
        // TODO: Reverse this so that isValueCompatible() uses this instead.
        return isValueCompatible(dataType.createFieldValue());
    }
Creates a new FieldValue of this type, with the given value.

@param arg the value of the new FieldValue
@return a new FieldValue of this type, with the given value
document/src/main/java/com/yahoo/document/DataType.java