How to use the sunpy.Grid.writeNC function in sunpy

"""
        Export the results to a netcdf file
        """
        from suntans_ugrid import ugrid
        from netCDF4 import Dataset
        
        # Fill in the depths with zero
        #if not self.__dict__.has_key('dv'):
        if dv==None:
            self.dv = np.zeros((self.Nc,))
        else:
            self.dv = dv
        if not self.__dict__.has_key('Nk'):
            self.Nk = self.Nkmax*np.ones((self.Nc,))
            
        Grid.writeNC(self,outfile)
        
        # write the time variable
        t= othertime.SecondsSince(self.time)
        self.create_nc_var(outfile,'time', ugrid['time']['dimensions'], ugrid['time']['attributes'])        
        
        # Create the other variables
        self.create_nc_var(outfile,'eta',('time','Nc'),{'long_name':'Sea surface elevation','units':'metres','coordinates':'time yv xv'})
        self.create_nc_var(outfile,'uc',('time','Nk','Nc'),{'long_name':'Eastward water velocity component','units':'metre second-1','coordinates':'time z_r yv xv'})
        self.create_nc_var(outfile,'vc',('time','Nk','Nc'),{'long_name':'Northward water velocity component','units':'metre second-1','coordinates':'time z_r yv xv'})
        self.create_nc_var(outfile,'salt',('time','Nk','Nc'),{'long_name':'Salinity','units':'ppt','coordinates':'time z_r yv xv'})
        self.create_nc_var(outfile,'temp',('time','Nk','Nc'),{'long_name':'Water temperature','units':'degrees C','coordinates':'time z_r yv xv'})
        self.create_nc_var(outfile,'agec',('time','Nk','Nc'),{'long_name':'Age concentration','units':''})
        self.create_nc_var(outfile,'agealpha',('time','Nk','Nc'),{'long_name':'Age alpha parameter','units':'seconds','coordinates':'time z_r yv xv'})
        self.create_nc_var(outfile,'agesource',('Nk','Nc'),\
        {'long_name':'Age source grid cell (>0 = source)',\
        'units':'','coordinates':'z_r yv xv'})