BUG: atomate2 0.0.23 ImportError 'LobsterSet' from 'pymatgen.io.vasp.sets'

# atomate2 0.0.23 ImportError: cannot import name 'LobsterSet' from 'pymatgen.io.vasp.sets' ## Issue Description atomate2 version 0.0.23 has an import error when trying to import `LobsterSet` from `pymatgen.io.vasp.sets`. This occurs because the latest version of pymatgen (2026.3.23) has removed or renamed the `LobsterSet` class, but atomate2 0.0.23 still attempts to import it. ## Steps to Reproduce 1. Install the latest versions: ```bash pip install atomate2==0.0.23 pip install pymatgen # installs 2026.3.23 ``` 2. Try to import atomate2: ```python from atomate2.vasp.flows.core import DoubleRelaxMaker ``` 3. Observe the import error: ``` ImportError: cannot import name 'LobsterSet' from 'pymatgen.io.vasp.sets' ``` ## Environment Information - **atomate2 version**: 0.0.23 - **pymatgen version**: 2026.3.23 - **Python version**: 3.12 - **Operating System**: Linux - **Installation method**: pip ## Expected Behavior atomate2 should import successfully without errors, or provide a clear error message if there are dependency conflicts. ## Actual Behavior Import fails with: ```python Traceback (most recent call last): File "/path/to/atomate2/vasp/flows/core.py", line 12, in <module> from atomate2.vasp.jobs.core import ( File "/path/to/atomate2/vasp/jobs/core.py", line 14, in <module> from atomate2.vasp.sets.core import ( File "/path/to/atomate2/vasp/sets/core.py", line 12, in <module> from pymatgen.io.vasp.sets import LobsterSet ImportError: cannot import name 'LobsterSet' from 'pymatgen.io.vasp.sets' (/path/to/pymatgen/io/vasp/sets.py) ``` ## Workaround Downgrade to compatible versions: ```bash pip install atomate2==0.0.22 pymatgen==2025.6.14 ``` This resolves the issue, but it's not a long-term solution. ## Root Cause Analysis The issue appears to be caused by: 1. **Version incompatibility**: atomate2 0.0.23 expects `LobsterSet` to exist in pymatgen 2. **API changes in pymatgen**: The latest pymatgen (2026.3.23) has removed or renamed `LobsterSet` 3. **Missing dependency constraints**: atomate2's dependencies don't properly constrain pymatgen versions ## Suggested Solutions ### Option 1: Update atomate2 to support latest pymatgen - Update the import statements to handle the absence of `LobsterSet` - Provide fallback or alternative implementations - Update dependency constraints in setup.py/pyproject.toml ### Option 2: Add proper dependency constraints - Add upper bound for pymatgen in atomate2's dependencies - Ensure compatibility with specific pymatgen versions - Provide clear version compatibility matrix ### Option 3: Graceful degradation - Make `LobsterSet` import optional - Provide clear error messages when dependencies are incompatible - Document version requirements clearly ## Additional Context This issue affects users who: - Install atomate2 from pip - Use the latest pymatgen version - Try to use atomate2 workflows for VASP calculations The workaround (downgrading) works but prevents users from benefiting from the latest pymatgen features and bug fixes. ## Priority **High** - This is a breaking change that prevents basic usage of atomate2 with current pymatgen versions. ## References - atomate2 version: 0.0.23 - pymatgen version: 2026.3.23 - Error location: `atomate2/vasp/sets/core.py` line 12