Make sure core examples run without error

bilby/core/likelihood.py

...ive_samplers/linear_regression_pymc3_custom_likelihood.py

examples/core_examples/conditional_prior.py

examples/core_examples/dirichlet.py

examples/core_examples/hyper_parameter_example.py

examples/core_examples/linear_regression_grid.py

examples/core_examples/occam_factor_example.py

examples/core_examples/radioactive_decay.py

examples/core_examples/slabspike_example.py

test/integration/example_test.py