How to use the hvplot.util.process_crs function in hvplot

if rot:
            axis = 'yrotation' if invert else 'xrotation'
            plot_opts[axis] = rot

        tools = list(tools) or list(plot_opts.get('tools', []))
        if hover is None:
            hover = not self.datashade
        if hover and not any(t for t in tools if isinstance(t, HoverTool)
                             or t == 'hover'):
            tools.append('hover')
        plot_opts['tools'] = tools

        if self.crs and global_extent:
            plot_opts['global_extent'] = global_extent
        if projection:
            plot_opts['projection'] = process_crs(projection)
        if title is not None:
            plot_opts['title_format'] = title
        if (self.kind in self._colorbar_types or self.rasterize or self.datashade or self._color_dim):
            try:
                if not use_dask:
                    symmetric = self._process_symmetric(symmetric, clim, check_symmetric_max)

                if self._style_opts.get('cmap') is None:
                    if symmetric:
                        self._style_opts['cmap'] = self._default_cmaps['diverging']
                    else:
                        self._style_opts['cmap'] = self._default_cmaps['linear']

                if symmetric is not None:
                    plot_opts['symmetric'] = symmetric
            except TypeError:

def _process_crs(self, data, crs):
        """Given crs as proj4 string, data.attr, or cartopy.crs return cartopy.crs
        """
        # get the proj string: either the value of data.attrs[crs] or crs itself
        _crs = getattr(data, 'attrs', {}).get(crs or 'crs', crs)
        try:
            return process_crs(_crs)
        except ValueError:
            # only raise error if crs was specified in kwargs
            if crs:
                raise ValueError(
                    "'{}' must be either a valid crs or an reference to "
                    "a `data.attr` containing a valid crs.".format(crs))

pos = nx.drawing.spring_layout

    if not isinstance(pos, dict):
        pos = pos(G, **kwargs.get('layout_kwargs', {}))

    params, label_params = {}, {}
    label_element = Labels
    if kwargs.get('geo', False) or 'crs' in kwargs:
        try:
            import geoviews
        except ImportError:
            raise ImportError('In order to use geo-related features '
                              'the geoviews library must be available. '
                              'It can be installed with:\n  conda '
                              'install -c pyviz geoviews')
        crs = process_crs(kwargs.get('crs'))
        label_element = geoviews.Labels
        params['cls'] = geoviews.Graph
        params['crs'] = crs
        label_params['crs'] = crs

    # Construct Graph object
    g = _from_networkx(G, pos, **params)

    if 'nodelist' in kwargs:
        g.nodes.data = g.nodes.data.iloc[list(kwargs['nodelist'])]

    if 'edgelist' in kwargs:
        edges = g.array([0, 1])
        comparisons = []
        for edge in kwargs['edgelist']:
            comparisons.append(edges == edge)