docs: def plot_mag_map_basemap(fignum, element, lons, lats, element_type, cmap='RdYlBu', lon_0=0, date=""):
      """
      makes a color contour map of geomagnetic field element
  
      Parameters
      ____________
      fignum : matplotlib figure number
      element : field element array from pmag.do_mag_map for plotting
      lons : longitude array from pmag.do_mag_map for plotting
      lats : latitude array from pmag.do_mag_map for plotting
      element_type : [B,Br,I,D] geomagnetic element type
          B : field intensity
          Br : radial field intensity
          I : inclinations
          D : declinations
      Optional
      _________
          cmap : matplotlib color map
          lon_0 : central longitude of the Hammer projection
          date : date used for field evaluation,
                 if custom ghfile was used, supply filename
  
  
      Effects
      ______________
      plots a Hammer projection color contour with  the desired field element
      """
      if not has_basemap:
          print('-W- Basemap must be installed to run plot_mag_map_basemap')
          return
      from matplotlib import cm  # matplotlib's color map module
      lincr = 1
      if type(date) != str:
          date = str(date)
      fig = plt.figure(fignum)
      m = Basemap(projection='hammer', lon_0=lon_0)
      x, y = m(*meshgrid(lons, lats))
      m.drawcoastlines()
      if element_type == 'B':
          levmax = element.max()+lincr
          levmin = round(element.min()-lincr)
          levels = np.arange(levmin, levmax, lincr)
          cs = m.contourf(x, y, element, levels=levels, cmap=cmap)
          plt.title('Field strength ($\mu$T): '+date)
      if element_type == 'Br':
          levmax = element.max()+lincr
          levmin = round(element.min()-lincr)
          cs = m.contourf(x, y, element, levels=np.arange(
              levmin, levmax, lincr), cmap=cmap)
          plt.title('Radial field strength ($\mu$T): '+date)
      if element_type == 'I':
          levmax = element.max()+lincr
          levmin = round(element.min()-lincr)
          cs = m.contourf(
              x, y, element, levels=np.arange(-90, 100, 20), cmap=cmap)
          m.contour(x, y, element, levels=np.arange(-80, 90, 10), colors='black')
          plt.title('Field inclination: '+date)
      if element_type == 'D':
          # cs=m.contourf(x,y,element,levels=np.arange(-180,180,10),cmap=cmap)
          cs = m.contourf(
              x, y, element, levels=np.arange(-180, 180, 10), cmap=cmap)
          m.contour(x, y, element, levels=np.arange(-180, 180, 10), colors='black')
          plt.title('Field declination: '+date)
      cbar = m.colorbar(cs, location='bottom')