docs: def plot_vgp(map_axis, vgp_lon=None, vgp_lat=None, di_block=None, label='', color='k', marker='o',
               edge='black', markersize=20, legend=False):
      """
      This function plots a paleomagnetic pole position on a cartopy map axis.
  
      Before this function is called, a plot needs to be initialized with code
      such as that in the make_orthographic_map function.
  
      Example
      -------
      >>> vgps = ipmag.fishrot(dec=200,inc=30)
      >>> vgp_lon_list,vgp_lat_list,intensities= ipmag.unpack_di_block(vgps)
      >>> map_axis = ipmag.make_orthographic_map(central_longitude=200,central_latitude=30)
      >>> ipmag.plot_vgp(map_axis,vgp_lon=vgp_lon_list,vgp_lat=vgp_lat_list,color='red',markersize=40)
  
      Required Parameters
      -----------
      map_axis : the name of the current map axis that has been developed using cartopy
      plon : the longitude of the paleomagnetic pole being plotted (in degrees E)
      plat : the latitude of the paleomagnetic pole being plotted (in degrees)
  
      Optional Parameters (defaults are used if not specified)
      -----------
      color : the color desired for the symbol (default is 'k' aka black)
      marker : the marker shape desired for the pole mean symbol (default is 'o' aka a circle)
      edge : the color of the edge of the marker (default is black)
      markersize : size of the marker in pt (default is 20)
      label : the default is no label. Labels can be assigned.
      legend : the default is no legend (False). Putting True will plot a legend.
      """
      if not has_cartopy:
          print('-W- cartopy must be installed to run ipmag.plot_vgp')
          return
      if di_block != None:
          di_lists = unpack_di_block(di_block)
          if len(di_lists) == 3:
              vgp_lon, vgp_lat, intensity = di_lists
          if len(di_lists) == 2:
              vgp_lon, vgp_lat = di_lists
      map_axis.scatter(vgp_lon, vgp_lat, marker=marker, edgecolors=[edge],
                       s=markersize, color=color, label=label, zorder=100, transform=ccrs.Geodetic())
      map_axis.set_global()
      if legend == True:
          plt.legend(loc=2)