public String filter(String base) {
		if ((base == null) || (base.length() < minLength)) {
			return null;
		}
		if (internalIndex >= 0) {
			return base.substring(0, internalIndex);
		}
		int len = base.length();
		return base.substring(len + internalIndex, len);//internalIndex is negative

	}
Applies filter to {@code base}
@param base the String to filter
@return The filtered {@link String}, or {@code null} if base does not meet the minimum length
requirement.
Ghidra/Features/BytePatterns/src/main/java/ghidra/bitpatterns/info/ByteSequenceLengthFilter.java