code: def test_help_style_extension_output(reset_default_backend):
      # default, after e.g. import hvplot.pandas
      docstring, signature = hvplot._get_doc_and_signature(
          cls=hvplot.hvPlot,
          kind="line",
          completions=False,
          docstring=False,
          generic=False,
          style=True,
          signature=None,
      )
      assert (
          docstring
          == "\nStyle options\n-------------\n\n"
          + "\n".join(sorted(Store.registry["bokeh"][Curve].style_opts))
      )
  
      # The current backend becomes matplotlib
      hvplot.extension("matplotlib", "plotly")
      docstring, signature = hvplot._get_doc_and_signature(
          cls=hvplot.hvPlot,
          kind="line",
          completions=False,
          docstring=False,
          generic=False,
          style=True,
          signature=None,
      )
      assert (
          docstring
          == "\nStyle options\n-------------\n\n"
          + "\n".join(
              sorted(Store.registry["matplotlib"][Curve].style_opts)
          )
      )
  
      # The current backend becomes plotly
      hvplot.output(backend="plotly")
      docstring, signature = hvplot._get_doc_and_signature(
          cls=hvplot.hvPlot,
          kind="line",
          completions=False,
          docstring=False,
          generic=False,
          style=True,
          signature=None,
      )
      assert (
          docstring
          == "\nStyle options\n-------------\n\n"
          + "\n".join(
              sorted(Store.registry["plotly"][Curve].style_opts)
          )
      )
  
imports: import hvplot.pandas
  import pytest
  from holoviews.core import Store
  from holoviews.element import Curve
label_desc: Use image node_id 2 for calling a global function with example usage: test_help_style_extension_output(reset_default_backend) without return types