Cpu memory optimization

[cehongwang]

Description

Delete the extra copy INetworkDefinition creates

Fixes # (issue)

Type of change

Please delete options that are not relevant and/or add your own.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified

[narendasan]

If we are doing this don't we end up paying the serialization cost again?

[cehongwang]

engine.serialize() does not take any memory.

with io.BytesIO() as engine_bytes:
                engine_bytes.write(serialized_engine)
                engine_str = engine_bytes.getvalue()

This does