@Override
	public void close() throws IOException {
		helperFunctionDefs = null;
		dtm.close();
	}
Ordered list of BPF helper functions.  Array index corresponds to helper ID.
A null may be substituted for a missing/unknown function definition. 

References:
  https://github.com/torvalds/linux/blob/master/include/uapi/linux/bpf.h
  https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
Ghidra/Processors/eBPF/src/main/java/ghidra/app/plugin/core/analysis/eBPFHelperDataTypes.java