BUG: yet another bug with saving data...

[eigenfoo]

It looks like #53 introduced yet another bug. I can't really figure out what's causing it though...

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-18-34b484f29cfd> in <module>()
      1 # Save the resulting trace object as a netcdf file.
----> 2 trace.save('contest_authors.nc')

~/bayesalpha/bayesalpha/base.py in save(self, filename, group, **args)
     13     def save(self, filename, group=None, **args):
     14         """Save the results to a netcdf file."""
---> 15         self._trace.to_netcdf(filename, group=group, **args)
     16 
     17     @classmethod

/opt/conda/lib/python3.6/site-packages/xarray/core/dataset.py in to_netcdf(self, path, mode, format, group, engine, encoding, unlimited_dims, compute)
   1148                          engine=engine, encoding=encoding,
   1149                          unlimited_dims=unlimited_dims,
-> 1150                          compute=compute)
   1151 
   1152     def to_zarr(self, store=None, mode='w-', synchronizer=None, group=None,

/opt/conda/lib/python3.6/site-packages/xarray/backends/api.py in to_netcdf(dataset, path_or_file, mode, format, group, engine, writer, encoding, unlimited_dims, compute)
    722     try:
    723         dataset.dump_to_store(store, sync=sync, encoding=encoding,
--> 724                               unlimited_dims=unlimited_dims, compute=compute)
    725         if path_or_file is None:
    726             return target.getvalue()

/opt/conda/lib/python3.6/site-packages/xarray/core/dataset.py in dump_to_store(self, store, encoder, sync, encoding, unlimited_dims, compute)
   1073 
   1074         store.store(variables, attrs, check_encoding,
-> 1075                     unlimited_dims=unlimited_dims)
   1076         if sync:
   1077             store.sync(compute=compute)

/opt/conda/lib/python3.6/site-packages/xarray/backends/common.py in store(self, variables, attributes, check_encoding_set, unlimited_dims)
    372         self.set_dimensions(variables, unlimited_dims=unlimited_dims)
    373         self.set_variables(variables, check_encoding_set,
--> 374                            unlimited_dims=unlimited_dims)
    375 
    376     def set_attributes(self, attributes):

/opt/conda/lib/python3.6/site-packages/xarray/backends/netCDF4_.py in set_variables(self, *args, **kwargs)
    405     def set_variables(self, *args, **kwargs):
    406         with self.ensure_open(autoclose=False):
--> 407             super(NetCDF4DataStore, self).set_variables(*args, **kwargs)
    408 
    409     def encode_variable(self, variable):

/opt/conda/lib/python3.6/site-packages/xarray/backends/common.py in set_variables(self, variables, check_encoding_set, unlimited_dims)
    411                 name, v, check, unlimited_dims=unlimited_dims)
    412 
--> 413             self.writer.add(source, target)
    414 
    415     def set_dimensions(self, variables, unlimited_dims=None):

/opt/conda/lib/python3.6/site-packages/xarray/backends/common.py in add(self, source, target)
    270             self.targets.append(target)
    271         else:
--> 272             target[...] = source
    273 
    274     def sync(self, compute=True):

/opt/conda/lib/python3.6/site-packages/xarray/backends/netCDF4_.py in __setitem__(self, key, value)
     46         with self.datastore.ensure_open(autoclose=True):
     47             data = self.get_array()
---> 48             data[key] = value
     49 
     50     def get_array(self):

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable.__setitem__()

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable._put()

TypeError: expected bytes, float found