def fit(self,train,item_features=None):
        max_iters,validation_iters,validation = self.create_validation_set(train)
        model = WARP(self.d,self.gamma,self.C,max_iters,validation_iters,self.batch_size,self.positive_thresh,self.max_trials)
        self.description = 'WARPMF({0})'.format(model)
        model.fit(train,validation)

        self.U = model.U_
        self.V = model.V_
Returns `True` if the given string is a valid email.  This calls
dataset/ETHPy150Open Mendeley/mrec/mrec/mf/warp.py/WARPMFRecommender.fit--crossover with--dataset/ETHPy150Open lsaffre/lino/lino/core/utils.py/is_valid_email