def get_emission_features(self, sequence, position, tag_id):
        raise NotImplementedError


#    def save_features(self,file):
#        fn = open(file,"w")
#        for feat_nr,feat in enumerate(self.feature_names):
#            fn.write("%i\t%s\n"%(feat_nr,feat))
#        fn.close()
#
#
#    ###########
#    # Loads all features form a file
#    ###########
#    def load_features(self,file,dataset):
#        fn = open(file)
#        self.feature_names = []
#        self.feature_dic = {}
#        for line in fn:
#            feat_nr,feat = line.strip().split("\t")
#            self.feature_names.append(feat)
#            self.feature_dic[feat] = int(feat_nr)
#        self.feature_list = []
#        self.nr_feats = len(self.feature_names)
#        self.add_features = False
#        self.dataset = dataset
#        fn.close()
#        #Speed up
#        self.node_feature_cache = {}
#        self.initial_state_feature_cache = {}
#        self.edge_feature_cache = {}
#        self.final_edge_feature_cache = {}
Returns all features for a node at position with tag_id
dataset/ETHPy150Open LxMLS/lxmls-toolkit/lxmls/sequences/bak/abstract_feature_class.py/AbstractFeatureClass.get_emission_features