Returns the variable for latitude

    :param netcdf4.dataset nc: an open netcdf dataset object

def get_lat_variable(nc):
    '''
    Returns the variable for latitude

    :param netcdf4.dataset nc: an open netcdf dataset object
    '''
    if 'latitude' in nc.variables:
        return 'latitude'
    latitudes = nc.get_variables_by_attributes(standard_name="latitude")
    if latitudes:
        return latitudes[0].name
    return None