Sampling the Banana-shaped distribution

I have tried another model and now I am getting the following ``[Errno 32] broken pipe’’ error:

BrokenPipeError                           Traceback (most recent call last)
<ipython-input-4-4bee32470d49> in <module>()
      4 with pm.Model() as pot1m:
      5     pm.DensityDist('pot1', logp=cust_logp, shape=(2,))
----> 6     trace1 = pm.sample(draws=10, step=pm.NUTS())
      7     #trace2 = pm.sample(10, step=pm.Metropolis())
      8 

~\Anaconda2\envs\python3.6\lib\site-packages\pymc3\sampling.py in sample(draws, step, init, n_init, start, trace, chain_idx, chains, cores, tune, nuts_kwargs, step_kwargs, progressbar, model, random_seed, live_plot, discard_tuned_samples, live_plot_kwargs, compute_convergence_checks, use_mmap, **kwargs)
    447             _print_step_hierarchy(step)
    448             try:
--> 449                 trace = _mp_sample(**sample_args)
    450             except pickle.PickleError:
    451                 _log.warning("Could not pickle model, sampling singlethreaded.")

~\Anaconda2\envs\python3.6\lib\site-packages\pymc3\sampling.py in _mp_sample(draws, tune, step, chains, cores, chain, random_seed, start, progressbar, trace, model, use_mmap, **kwargs)
    994         sampler = ps.ParallelSampler(
    995             draws, tune, chains, cores, random_seed, start, step,
--> 996             chain, progressbar)
    997         try:
    998             with sampler:

~\Anaconda2\envs\python3.6\lib\site-packages\pymc3\parallel_sampling.py in __init__(self, draws, tune, chains, cores, seeds, start_points, step_method, start_chain_num, progressbar)
    273             ProcessAdapter(draws, tune, step_method,
    274                            chain + start_chain_num, seed, start)
--> 275             for chain, seed, start in zip(range(chains), seeds, start_points)
    276         ]
    277 

~\Anaconda2\envs\python3.6\lib\site-packages\pymc3\parallel_sampling.py in <listcomp>(.0)
    273             ProcessAdapter(draws, tune, step_method,
    274                            chain + start_chain_num, seed, start)
--> 275             for chain, seed, start in zip(range(chains), seeds, start_points)
    276         ]
    277 

~\Anaconda2\envs\python3.6\lib\site-packages\pymc3\parallel_sampling.py in __init__(self, draws, tune, step_method, chain, seed, start)
    180             draws, tune, seed)
    181         # We fork right away, so that the main process can start tqdm threads
--> 182         self._process.start()
    183 
    184     @property

~\Anaconda2\envs\python3.6\lib\multiprocessing\process.py in start(self)
    103                'daemonic processes are not allowed to have children'
    104         _cleanup()
--> 105         self._popen = self._Popen(self)
    106         self._sentinel = self._popen.sentinel
    107         # Avoid a refcycle if the target function holds an indirect

~\Anaconda2\envs\python3.6\lib\multiprocessing\context.py in _Popen(process_obj)
    221     @staticmethod
    222     def _Popen(process_obj):
--> 223         return _default_context.get_context().Process._Popen(process_obj)
    224 
    225 class DefaultContext(BaseContext):

~\Anaconda2\envs\python3.6\lib\multiprocessing\context.py in _Popen(process_obj)
    320         def _Popen(process_obj):
    321             from .popen_spawn_win32 import Popen
--> 322             return Popen(process_obj)
    323 
    324     class SpawnContext(BaseContext):

~\Anaconda2\envs\python3.6\lib\multiprocessing\popen_spawn_win32.py in __init__(self, process_obj)
     63             try:
     64                 reduction.dump(prep_data, to_child)
---> 65                 reduction.dump(process_obj, to_child)
     66             finally:
     67                 set_spawning_popen(None)

~\Anaconda2\envs\python3.6\lib\multiprocessing\reduction.py in dump(obj, file, protocol)
     58 def dump(obj, file, protocol=None):
     59     '''Replacement for pickle.dump() using ForkingPickler.'''
---> 60     ForkingPickler(file, protocol).dump(obj)
     61 
     62 #

BrokenPipeError: [Errno 32] Broken pipe

Thank you for your help!