'Convert the query string filter op shorthand into actual ORM usable
function names, then return the ORM function.'

def _convert_op_string_to_fn(self, column, op_string):

    fn_name = op_string
    if (op_string in self.UNDERSCORED_OPS):
        fn_name = (('__' + op_string) + '__')
    elif (op_string == 'in'):
        fn_name = 'in_'
    op_fn = getattr(column, fn_name, None)
    if ((not op_fn) or (not callable(op_fn))):
        return None
    return op_fn
