code: def get_statistics(self):
          
          statistics = {
              "number_authors": 0,
              "number_author_names": 0,
              "number_author_abbreviations": 0,
              "number_works": 0,
              "number_work_titles": 0,
              "number_title_abbreviations": 0,
              "number_opus_maximum":0,
          }
          for author in self.get_authors():
              if author.get_urn() is not None:
                  opmax = True if self.get_opus_maximum_of(author.get_urn())\
                      is not None else False
                  if opmax:
                      statistics["number_opus_maximum"] += 1
              statistics["number_authors"] += 1
              statistics["number_author_names"] += len(author.get_names())
              statistics["number_author_abbreviations"] += len(
                  author.get_abbreviations()
              )
              for work in author.get_works():
                  statistics["number_works"] += 1
                  statistics["number_work_titles"] += len(work.get_titles())
                  statistics["number_title_abbreviations"] += len(
                      work.get_abbreviations()
                  )
          return statistics
docs: Gather basic stats about the Knowledge Base and its contents.
  
          :return: a dictionary