def check_lat_lon_in_dataset(ds_ext, lat, lon):
    """
    Checks for the presence of the specified latitude, longitude in the provided dataset
    Input:
         - ds     : the xarray dataset 
         - lat    : latitude 
         - lon    : longitude         
    Returns: status (boolean) and message (str). True, if the both exist in the coordinates. Else, False with apprpriate message.
    """
    err_msg = ''
    
    start_lat = ds_ext.coords['lat'].item(0)
    end_lat = ds_ext.coords['lat'].item(-1)
    start_lon = ds_ext.coords['lon'].item(0)
    end_lon = ds_ext.coords['lon'].item(-1)
    
    if not (start_lat <= lat and end_lat >= lat):
        err_msg = 'Latitude {} outside the dataset coordinates range of lat: {} to {}'.format(lat, start_lat, end_lat)
    if not (start_lon <= lon and end_lon >= lon):
        err_msg = 'Longitude {} outside the dataset coordinates range of lon: {} to {}'.format(lon, start_lon, end_lon)
    if err_msg == '':
        return True, ''
    else:
        return False, err_msg