Add module-level docstrings and helper utility docstrings

Co-authored-by: varun-r-mallya <100590632+varun-r-mallya@users.noreply.github.com>

pythonbpf/functions/functions_pass.py

@@ -1,3 +1,11 @@
+"""
+BPF function processing and LLVM IR generation.
+
+This module handles the core function processing, converting Python function
+definitions into LLVM IR for BPF programs. It manages local variables,
+control flow, and statement processing.
+"""
+
 from llvmlite import ir
 import ast
 import logging