class_docstr: Main class; contains all subelements: book -> page -> block -> par -> line -> format
class_docstr_tok: ["Main","class",";","contains","all","subelements",":","book","-",">","page","-",">","block","-",">","par","-",">","line","-",">","format"]
code: def __init__(self):
      self.pages = []
  
label_desc: Use image node_id 1 to create a new Book object  with example: obj = Book()