Traceback (most recent call last):
  File "/home/jforbes/ytscripts/cloud.py", line 211, in <module>
    main(slices,phase,chk,clumps)
  File "/home/jforbes/ytscripts/cloud.py", line 86, in main
    amods.level_sets.write_clump_hierarchy(master_clump,0,f)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/analysis_modules/level_sets/clump_handling.py", line 221, in write_clump_hierarchy
    clump.write_info(level,f_ptr)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/analysis_modules/level_sets/clump_handling.py", line 109, in write_info
    value = eval(item['quantity'])
  File "<string>", line 1, in <module>
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/derived_quantities.py", line 92, in __call__
    return self._call_func_lazy(args, kwargs)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/derived_quantities.py", line 99, in _call_func_lazy
    rv = self.func(GridChildMaskWrapper(g, self._data_source), *args, **kwargs)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/derived_quantities.py", line 203, in _WeightedAverageQuantity
    num = (data[field] * data[weight]).sum()
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/derived_quantities.py", line 60, in __getitem__
    data = self.data_source._get_data_from_grid(self.grid, item)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/data_containers.py", line 95, in save_state
    tr = func(self, grid, field, *args, **kwargs)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/data_containers.py", line 2645, in _get_data_from_grid
    tr = grid[field]
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 157, in __getitem__
    self.get_data(key)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 200, in get_data
    self._generate_field(field)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 145, in _generate_field
    self[field] = self.pf.field_info[field](self)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/field_info_container.py", line 395, in __call__
    dd = self._function(self, data)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/universal_fields.py", line 981, in _JeansMassMsun
    ((data["Temperature"]/data["MeanMolecularWeight"])**(1.5)) *
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 157, in __getitem__
    self.get_data(key)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 200, in get_data
    self._generate_field(field)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 145, in _generate_field
    self[field] = self.pf.field_info[field](self)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/field_info_container.py", line 395, in __call__
    dd = self._function(self, data)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/universal_fields.py", line 973, in _MeanMolecularWeight
    return (data["Density"] / (mh *data["NumberDensity"]))
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 157, in __getitem__
    self.get_data(key)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 200, in get_data
    self._generate_field(field)
  File "/home/jforbes/yt-x86_64/src/yt-hg/yt/data_objects/grid_patch.py", line 147, in _generate_field
    raise exceptions.KeyError(field)
KeyError: 'NumberDensity'