1.15.0: last release declaring Python 3.9 and 3.10

Last GPy release that declares Python 3.9 and 3.10. Binary wheels stay 3.11–3.14, as in 1.14.x. The next minor will require Python ≥ 3.11 (Discussion #1207).

Install: pip install gpy==1.15.0
Plots: pip install 'gpy[plotting]'

Packaging and platforms

• Switch the build to Poetry (CIP-0003). Cython extensions are built at install time; generated C is not shipped.
• Publish manylinux aarch64 wheels beside x86_64, plus macOS and Windows.
• import GPy no longer fails if matplotlib or plotly is missing (#1209).

Library

• Plotting: pylab → pyplot; Plotly subplots/traces updated (#1210).
• Serialization and model reload: pickle of linked kernels (#605), WarpedGP / SparseGPRegression save/load, README reload via m[:] = loaded (#1217).
• Correctness: EP after optimize_restarts (#1109), Student-t full covariance (#993), heteroscedastic set_XY (#959), Uniform / HalfT / Exponential priors, Gamma Laplace gradients (#1037), several likelihood predict paths under NumPy 2.
• Wiener Velocity kernel (#1003). Periodic and coregionalize to_dict / from_dict.

Docs and process

• Tutorial notebooks in SheffieldML/notebook now execute against this candidate (Python 3 / NumPy 2).
• Contributor poetry.lock refresh for Dependabot; 3.9/3.10 pins stay where no patched wheel exists.
• Full item list: CHANGELOG.