'Construct URL query variable(s) name from a filter query
selector and the given operator(s)
@param selector: the selector
@param operator: the operator (or tuple/list of operators)
@return: the URL query variable name (or list of variable names)'

@classmethod
def _variable(cls, selector, operator):

    selectors = selector.split('|')
    return [('%s__%s' % (selector, operator)) for selector in selectors]
