title: Saving a holoviews plot as an SVG
body: <p>I would like to save a holoviews plot as a SVG, however I am getting an error message that I don't understand:</p>
  <pre><code>    np.random.seed(9)
      data = np.random.rand(10, 2)
      points = hv.Points(data)
      labels = hv.Labels({('x', 'y'): data, 'text': [chr(65+i) for i in range(10)]}, ['x', 'y'], 'text')
      overlay = (points * labels).redim.range(x=(-0.2, 1.2), y=(-.2, 1.2))
      
      overlay.opts(
          opts.Labels(text_font_size='10pt', xoffset=0.08),
          opts.Points(color='black', size=5))
      
      hv.save(overlay, 'overlay.svg', fmt='svg')
  </code></pre>
  <pre><code>    ---------------------------------------------------------------------------
      Exception                                 Traceback (most recent call last)
      &lt;ipython-input-29-b23ca97e9c01&gt; in &lt;module&gt;
            9     opts.Points(color='black', size=5))
           10 
      ---&gt; 11 hv.save(overlay, 'overlay.svg', fmt='svg')
      
      ~/miniconda3/envs/mybrew/lib/python3.7/site-packages/holoviews/util/__init__.py in save(obj, filename, fmt, backend, resources, toolbar, title, **kwargs)
          818             filename = '.'.join(formats[:-1])
          819     return renderer_obj.save(obj, filename, fmt=fmt, resources=resources,
      --&gt; 820                              title=title)
          821 
          822 
      
      ~/miniconda3/envs/mybrew/lib/python3.7/site-packages/holoviews/plotting/renderer.py in save(self_or_cls, obj, basename, fmt, key, info, options, resources, title, **kwargs)
          592 
          593         with StoreOptions.options(obj, options, **kwargs):
      --&gt; 594             plot, fmt = self_or_cls._validate(obj, fmt)
          595 
          596         if isinstance(plot, Viewable):
      
      ~/miniconda3/envs/mybrew/lib/python3.7/site-packages/holoviews/plotting/renderer.py in _validate(self, obj, fmt, **kwargs)
          302         if fmt not in all_formats:
          303             raise Exception(&quot;Format %r not supported by mode %r. Allowed formats: %r&quot;
      --&gt; 304                             % (fmt, self.mode, fig_formats + holomap_formats))
          305         self.last_plot = plot
          306         return plot, fmt
      
      Exception: Format 'svg' not supported by mode 'default'. Allowed formats: ['html', 'auto', 'png', 'widgets', 'scrubber', 'gif', 'auto', None]
  </code></pre>
  <p>Would anyone have a clue why this might be happening? According to the docs:</p>
  <p><a href="http://holoviews.org/user_guide/Exporting_and_Archiving.html" rel="noreferrer">http://holoviews.org/user_guide/Exporting_and_Archiving.html</a></p>
  <p>export to SVG should be possible.</p>