docs: def _read_latex_files(self):
          '''
          Check if some latex output files exist
          before first latex run, process them and return
          the generated data.
  
              - Parsing *.aux for citations counter and
                existing glossaries.
              - Getting content of files to detect changes.
                  - *.toc file
                  - all available glossaries files
          '''
          if os.path.isfile('%s.aux' % self.project_name):
              cite_counter = self.generate_citation_counter()
              self.read_glossaries()
          else:
              cite_counter = {'%s.aux' % self.project_name:
                              defaultdict(int)}
  
          fname = '%s.toc' % self.project_name
          if os.path.isfile(fname):
              with open(fname) as fobj:
                  toc_file = fobj.read()
          else:
              toc_file = ''
  
          gloss_files = dict()
          for gloss in self.glossaries:
              ext = self.glossaries[gloss][1]
              filename = '%s.%s' % (self.project_name, ext)
              if os.path.isfile(filename):
                  with open(filename) as fobj:
                      gloss_files[gloss] = fobj.read()
  
          return cite_counter, toc_file, gloss_files