Phase 3: Parse - Refactor to Polars

[mattsan-dev]

Overview
The normalise step now produces data using Polars LazyFrames, but the parse step still uses the legacy implementation and cannot process this new output. To keep the pipeline consistent and efficient, the parse phase must be updated to use the Polars version. This will keep existing behaviour while modernising the underlying process.

Tech Approach

• Update digital_land/phase/parse.py so it delegates to the Polars parse implementation.
• Implement the full parse logic inside digital_land/phase_polars/transform/parse.py.
• Convert existing parse rules into Polars lazy transformations.
• Ensure the parse phase accepts the LazyFrame produced by the new normalise step.
• Keep the same public interface so no downstream code needs changing.

Useful references:
phase_polars/transform/normalise.py
phase_polars/transform/parse.py
phase/parse.py
Polars LazyFrame documentation

Acceptance Criteria/Tests

• Parse phase accepts the normalise phase LazyFrame without errors.
• Legacy parse behaviour is reproduced using Polars.
• Outputs match the legacy parse phase (apart from expected improvements).
• No Pandas or row‑based Python operations are used.
• Add test cases
• Refactored code complies with project formatting and style standards (black/flake8/pep)

Resourcing & Dependencies
Depends on Normalise, no external teams.

[lakshmi-kovvuri1]

After passing polars lazy frame to parse polars_parse phase , the new entry_number is added to the dataframe

[lakshmi-kovvuri1]

@VENKAT-AVVARI-190825 please create unitests. for the polars_parse phase
1.digital_land/phase_polars/transform/parse.py
2. Please also update the code for black( flake8 formatting)