SUPPLEMENT SPAN,

gold data: IOB(inside-outside-beginning) format or BIO

quote from this link https://towardsdatascience.com/named-entity-recognition-and-classification-with-scikit-learn-f05372f07ba2

The IOB (short for inside, outside, beginning) is a common tagging format for tagging tokens. I- prefix before a tag indicates that the tag is inside a chunk. B- prefix before a tag indicates that the tag is the beginning of a chunk. An O tag indicates that a token belongs to no chunk (outside).

Types of named entities in gold data: {'B-MISC', 'I-LOC', 'I-MISC', 'I-ORG', 'I-PER', 'O'}