Explicit null checks

Always use explicit null checks (value is None or value is not None) rather than implicit truthiness evaluations when testing for null/None values. Implicit boolean checks can invoke __bool__ methods leading to unexpected behavior.

Do this:

# Explicitly check if out is not None
if out is not None:
    # Use out
    process(out)

Not this:

# Don't rely on truthiness which may call __bool__
if out:
    # May not behave as expected if __bool__ is implemented
    process(out)

For complex types that can represent optional values, use proper optional type wrappers:

In C++:

// Use optional wrappers for nullable types
'float or None': 'dmlc::optional<float>'  // Instead of just 'mx_float'

When handling values that might have multiple return types or be null:

# Check the specific type before processing
if isinstance(out, NDArrayBase):
    return out
return list(out)  # Convert if needed