tokens: Currently , when I use " tf.contrib.crf.crf_log_likelihood " to calculate the loss function , it gives the error " Second-order gradient for while loops not supported " .
ner_tags: O O O O O O B-Code_Block O O O O O O O O O O O B-Output_Block I-Output_Block I-Output_Block I-Output_Block I-Output_Block I-Output_Block I-Output_Block I-Output_Block I-Output_Block O