viterbi sequence-prediction pos-tags scikit-learn neural-networks conditional-random-fields NER word2vec syntactic-dependencies evaluation_metrics document-classification classification SyntaxNet NLTK word-embeddings tokenization tf-idf stanford-NER relationship-extraction named-entity-recognition naive-bayes multi-label-classification maximum-entropy-markov-models logistic-regression language-models information-extraction imbalanced_data hyperparameter-optimization hidden-markov-models grid-search glove gensim fasttext doc2vec dependency-graph deep-learning convolutional-neural-networks character-language-models character-embeddings PyData LSTM ELMo BERT