Export `code_table` named constants from top-level `__init__.py`

[sumanjeet0012]

Named constants like SHA2_256, DAG_CBOR, IP4 etc. from code_table.py are not re-exported from the top-level multicodec package. Users must import from a submodule (from multicodec.code_table import SHA2_256) instead of the top-level package.

Problem

Current usage requires a submodule import:

# Current: requires submodule import
from multicodec.code_table import SHA2_256, DAG_CBOR, IP4

All other public symbols (Code, prefix functions, serialization, etc.) are available from the top-level package:

# Everything else is top-level
from multicodec import Code, add_prefix, get_codec, encode, decode

This inconsistency means users need to know about the internal module structure to use named constants.

Proposed Solution

There are two options:

Option A: Re-export the most commonly used constants from __init__.py:

from .code_table import (
    IDENTITY, SHA1, SHA2_256, SHA2_512, SHA3_256, SHA3_512,
    DAG_PB, DAG_CBOR, DAG_JSON, RAW,
    IP4, IP6, TCP, UDP,
)

Option B: Keep them in the submodule but add a prominent note in the docs and README:

# Recommended import pattern
from multicodec.code_table import SHA2_256

Recommended: Option A with a curated set of ~20 most-used constants, plus a note that from multicodec.code_table import * is available for all 603.

Update __all__ accordingly.

Related

• File: multicodec/__init__.py
• Constants source: multicodec/code_table.py (603 constants)