hvplot.labels: TypeError: '<' not supported between instances of 'str' and 'int'

hvplot==0.8.1

A colleague of mine was trying to add labels to her plot. She got an exception that was hard to find the cause of. The problem was that she was using *heterogenous* data as text labels.

Here is a minimum, reproducible example.

```python
import hvplot.pandas
import pandas as pd

df = pd.DataFrame({
"x": [1,2],
"y": [3,4],
"text": [0, "+1"],
})
df.hvplot.labels(x="x", y="y", text="text")
```

```bash
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
File /opt/conda/lib/python3.10/site-packages/IPython/core/formatters.py:972, in MimeBundleFormatter.__call__(self, obj, include, exclude)
969 method = get_real_method(obj, self.print_method)
971 if method is not None:
--> 972 return method(include=include, exclude=exclude)
973 return None
974 else:

File /opt/conda/lib/python3.10/site-packages/holoviews/core/dimension.py:1294, in Dimensioned._repr_mimebundle_(self, include, exclude)
1287 def _repr_mimebundle_(self, include=None, exclude=None):
1288 """
1289 Resolves the class hierarchy for the class rendering the
1290 object using any display hooks registered on Store.display
1291 hooks. The output of all registered display_hooks is then
1292 combined and returned.
1293 """
-> 1294 return Store.render(self)

File /opt/conda/lib/python3.10/site-packages/holoviews/core/options.py:1426, in Store.render(cls, obj)
1424 data, metadata = {}, {}
1425 for hook in hooks:
-> 1426 ret = hook(obj)
1427 if ret is None:
1428 continue

File /opt/conda/lib/python3.10/site-packages/holoviews/ipython/display_hooks.py:277, in pprint_display(obj)
275 if not ip.display_formatter.formatters['text/plain'].pprint:
276 return None
--> 277 return display(obj, raw_output=True)

File /opt/conda/lib/python3.10/site-packages/holoviews/ipython/display_hooks.py:247, in display(obj, raw_output, **kwargs)
245 elif isinstance(obj, (CompositeOverlay, ViewableElement)):
246 with option_state(obj):
--> 247 output = element_display(obj)
248 elif isinstance(obj, (Layout, NdLayout, AdjointLayout)):
249 with option_state(obj):

File /opt/conda/lib/python3.10/site-packages/holoviews/ipython/display_hooks.py:141, in display_hook..wrapped(element)
139 try:
140 max_frames = OutputSettings.options['max_frames']
--> 141 mimebundle = fn(element, max_frames=max_frames)
142 if mimebundle is None:
143 return {}, {}

File /opt/conda/lib/python3.10/site-packages/holoviews/ipython/display_hooks.py:187, in element_display(element, max_frames)
184 if type(element) not in Store.registry[backend]:
185 return None
--> 187 return render(element)

File /opt/conda/lib/python3.10/site-packages/holoviews/ipython/display_hooks.py:68, in render(obj, **kwargs)
65 if renderer.fig == 'pdf':
66 renderer = renderer.instance(fig='png')
---> 68 return renderer.components(obj, **kwargs)

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/renderer.py:398, in Renderer.components(self, obj, fmt, comm, **kwargs)
395 embed = (not (dynamic or streams or self.widget_mode == 'live') or config.embed)
397 if embed or config.comms == 'default':
--> 398 return self._render_panel(plot, embed, comm)
399 return self._render_ipywidget(plot)

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/renderer.py:405, in Renderer._render_panel(self, plot, embed, comm)
403 doc = Document()
404 with config.set(embed=embed):
--> 405 model = plot.layout._render_model(doc, comm)
406 if embed:
407 return render_model(model, comm)

File /opt/conda/lib/python3.10/site-packages/panel/viewable.py:507, in Renderable._render_model(self, doc, comm)
505 if comm is None:
506 comm = state._comm_manager.get_server_comm()
--> 507 model = self.get_root(doc, comm)
509 if config.embed:
510 embed_state(self, model, doc,
511 json=config.embed_json,
512 json_prefix=config.embed_json_prefix,
513 save_path=config.embed_save_path,
514 load_path=config.embed_load_path,
515 progress=False)

File /opt/conda/lib/python3.10/site-packages/panel/viewable.py:558, in Renderable.get_root(self, doc, comm, preprocess)
541 """
542 Returns the root model and applies pre-processing hooks
543
(...)
555 Returns the bokeh model corresponding to this panel object
556 """
557 doc = init_doc(doc)
--> 558 root = self._get_model(doc, comm=comm)
559 if preprocess:
560 self._preprocess(root)

File /opt/conda/lib/python3.10/site-packages/panel/layout/base.py:146, in Panel._get_model(self, doc, root, parent, comm)
144 if root is None:
145 root = model
--> 146 objects = self._get_objects(model, [], doc, root, comm)
147 props = dict(self._init_params(), objects=objects)
148 model.update(**self._process_param_change(props))

File /opt/conda/lib/python3.10/site-packages/panel/layout/base.py:131, in Panel._get_objects(self, model, old_objects, doc, root, comm)
129 else:
130 try:
--> 131 child = pane._get_model(doc, root, model, comm)
132 except RerenderError:
133 return self._get_objects(model, current_objects[:i], doc, root, comm)

File /opt/conda/lib/python3.10/site-packages/panel/pane/holoviews.py:248, in HoloViews._get_model(self, doc, root, parent, comm)
246 plot = self.object
247 else:
--> 248 plot = self._render(doc, comm, root)
250 plot.pane = self
251 backend = plot.renderer.backend

File /opt/conda/lib/python3.10/site-packages/panel/pane/holoviews.py:324, in HoloViews._render(self, doc, comm, root)
321 if comm:
322 kwargs['comm'] = comm
--> 324 return renderer.get_plot(self.object, **kwargs)

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/bokeh/renderer.py:70, in BokehRenderer.get_plot(self_or_cls, obj, doc, renderer, **kwargs)
63 @bothmethod
64 def get_plot(self_or_cls, obj, doc=None, renderer=None, **kwargs):
65 """
66 Given a HoloViews Viewable return a corresponding plot instance.
67 Allows supplying a document attach the plot to, useful when
68 combining the bokeh model with another plot.
69 """
---> 70 plot = super().get_plot(obj, doc, renderer, **kwargs)
71 if plot.document is None:
72 plot.document = Document() if self_or_cls.notebook_context else curdoc()

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/renderer.py:240, in Renderer.get_plot(self_or_cls, obj, doc, renderer, comm, **kwargs)
237 defaults = [kd.default for kd in plot.dimensions]
238 init_key = tuple(v if d is None else d for v, d in
239 zip(plot.keys[0], defaults))
--> 240 plot.update(init_key)
241 else:
242 plot = obj

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/plot.py:948, in DimensionedPlot.update(self, key)
946 def update(self, key):
947 if len(self) == 1 and ((key == 0) or (key == self.keys[0])) and not self.drawn:
--> 948 return self.initialize_plot()
949 item = self.__getitem__(key)
950 self.traverse(lambda x: setattr(x, '_updated', True))

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/bokeh/element.py:1380, in ElementPlot.initialize_plot(self, ranges, plot, plots, source)
1378 element = self.hmap.last
1379 key = util.wrap_tuple(self.hmap.last_key)
-> 1380 ranges = self.compute_ranges(self.hmap, key, ranges)
1381 self.current_ranges = ranges
1382 self.current_frame = element

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/plot.py:607, in DimensionedPlot.compute_ranges(self, obj, key, ranges)
603 # Only compute ranges if not axiswise on a composite plot
604 # or not framewise on a Overlay or ElementPlot
605 if (not (axiswise and not isinstance(obj, HoloMap)) or
606 (not framewise and isinstance(obj, HoloMap))):
--> 607 self._compute_group_range(group, elements, ranges, framewise,
608 axiswise, robust, self.top_level,
609 prev_frame)
610 self.ranges.update(ranges)
611 return ranges

File /opt/conda/lib/python3.10/site-packages/holoviews/plotting/plot.py:717, in DimensionedPlot._compute_group_range(cls, group, elements, ranges, framewise, axiswise, robust, top_level, prev_frame)
715 data_range = ds.range(el_dim, dimension_range=False)
716 else:
--> 717 data_range = el.range(el_dim, dimension_range=False)
719 data_ranges[(el, el_dim)] = data_range
720 if dtype is not None and dtype.kind == 'uif' and robust:

File /opt/conda/lib/python3.10/site-packages/holoviews/core/data/__init__.py:204, in PipelineMeta.pipelined..pipelined_fn(*args, **kwargs)
201 inst._in_method = True
203 try:
--> 204 result = method_fn(*args, **kwargs)
205 if PipelineMeta.disable:
206 return result

File /opt/conda/lib/python3.10/site-packages/holoviews/core/data/__init__.py:515, in Dataset.range(self, dim, data_range, dimension_range)
513 return dim.range
514 elif dim in self.dimensions() and data_range and bool(self):
--> 515 lower, upper = self.interface.range(self, dim)
516 else:
517 lower, upper = (np.NaN, np.NaN)

File /opt/conda/lib/python3.10/site-packages/holoviews/core/data/pandas.py:179, in PandasInterface.range(cls, dataset, dimension)
177 column = column.sort(inplace=False)
178 else:
--> 179 column = column.sort_values()
180 try:
181 column = column[~column.isin([None, pd.NA])]

File /opt/conda/lib/python3.10/site-packages/pandas/util/_decorators.py:331, in deprecate_nonkeyword_arguments..decorate..wrapper(*args, **kwargs)
325 if len(args) > num_allow_args:
326 warnings.warn(
327 msg.format(arguments=_format_argument_list(allow_args)),
328 FutureWarning,
329 stacklevel=find_stack_level(),
330 )
--> 331 return func(*args, **kwargs)

File /opt/conda/lib/python3.10/site-packages/pandas/core/series.py:3768, in Series.sort_values(self, axis, ascending, inplace, kind, na_position, ignore_index, key)
3766 # GH 35922. Make sorting stable by leveraging nargsort
3767 values_to_sort = ensure_key_mapped(self, key)._values if key else self._values
-> 3768 sorted_index = nargsort(values_to_sort, kind, bool(ascending), na_position)
3770 result = self._constructor(
3771 self._values[sorted_index], index=self.index[sorted_index]
3772 )
3774 if ignore_index:

File /opt/conda/lib/python3.10/site-packages/pandas/core/sorting.py:438, in nargsort(items, kind, ascending, na_position, key, mask)
436 non_nans = non_nans[::-1]
437 non_nan_idx = non_nan_idx[::-1]
--> 438 indexer = non_nan_idx[non_nans.argsort(kind=kind)]
439 if not ascending:
440 indexer = indexer[::-1]

TypeError: '<' not supported between instances of 'str' and 'int'
```