I am trying to understand how to use pm.DensityDist. From the source code there are example and I followed it with just a little bit change: Here is my code:

```
import pymc3 as pm
import numpy as np
import scipy.stats as ss
with pm.Model():
mu = pm.Normal('mu', 0 , 1)
normal_dist = pm.Normal.dist(mu, 1)
dens = pm.DensityDist(
'density_dist',
normal_dist.logp,
observed=np.random.randn(100),
random=ss.norm.rvs,
)
prior = pm.sample_prior_predictive(10)['density_dist']
```

However I got an error “TypeError: _parse_args_rvs() got an unexpected keyword argument ‘point’”. Here is the detail:

```
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in _draw_value(param, point, givens, size)
807 try:
--> 808 return dist_tmp.random(point=point, size=size)
809 except (ValueError, TypeError):
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in random(self, point, size, **kwargs)
392 size=None,
--> 393 not_broadcast_kwargs=not_broadcast_kwargs,
394 )
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in generate_samples(generator, *args, **kwargs)
966 if dist_bcast_shape[:len(size_tup)] == size_tup:
--> 967 samples = generator(size=dist_bcast_shape, *args, **kwargs)
968 else:
~/miniconda3/envs/ppl/lib/python3.7/site-packages/scipy/stats/_distn_infrastructure.py in rvs(self, *args, **kwds)
958 rndm = kwds.pop('random_state', None)
--> 959 args, loc, scale, size = self._parse_args_rvs(*args, **kwds)
960 cond = logical_and(self._argcheck(*args), (scale >= 0))
TypeError: _parse_args_rvs() got an unexpected keyword argument 'point'
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
<ipython-input-1-ee9edf2b0ada> in <module>
13 random=ss.norm.rvs,
14 )
---> 15 prior = pm.sample_prior_predictive(10)['density_dist']
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/sampling.py in sample_prior_predictive(samples, model, vars, var_names, random_seed)
1384 names = get_default_varnames(vars_, include_transformed=False)
1385 # draw_values fails with auto-transformed variables. transform them later!
-> 1386 values = draw_values([model[name] for name in names], size=samples)
1387
1388 data = {k: v for k, v in zip(names, values)}
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in draw_values(params, point, size)
625 point=point,
626 givens=temp_givens,
--> 627 size=size)
628 givens[next_.name] = (next_, value)
629 drawn[(next_, size)] = value
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in _draw_value(param, point, givens, size)
815 with _DrawValuesContextBlocker():
816 val = np.atleast_1d(dist_tmp.random(point=point,
--> 817 size=None))
818 # Sometimes point may change the size of val but not the
819 # distribution's shape
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in random(self, point, size, **kwargs)
391 self.rand,
392 size=None,
--> 393 not_broadcast_kwargs=not_broadcast_kwargs,
394 )
395 test_shape = test_draw.shape
~/miniconda3/envs/ppl/lib/python3.7/site-packages/pymc3/distributions/distribution.py in generate_samples(generator, *args, **kwargs)
965 )
966 if dist_bcast_shape[:len(size_tup)] == size_tup:
--> 967 samples = generator(size=dist_bcast_shape, *args, **kwargs)
968 else:
969 samples = generator(size=size_tup + dist_bcast_shape, *args, **kwargs)
~/miniconda3/envs/ppl/lib/python3.7/site-packages/scipy/stats/_distn_infrastructure.py in rvs(self, *args, **kwds)
957 discrete = kwds.pop('discrete', None)
958 rndm = kwds.pop('random_state', None)
--> 959 args, loc, scale, size = self._parse_args_rvs(*args, **kwds)
960 cond = logical_and(self._argcheck(*args), (scale >= 0))
961 if not np.all(cond):
TypeError: _parse_args_rvs() got an unexpected keyword argument 'point'.
```

I am not so sure is it bug in pymc3, scipy, or my code is just wrong. Is there anyone who can help me?