code: def find_input_documents(self):
          
          paths = []
          itr = chain(texutils.input_pattern.finditer(self.text),
                      texutils.input_ifexists_pattern.finditer(self.text))
          for match in itr:
              fname = match.group(1)
              if not fname.endswith('.tex'):
                  full_fname = ".".join((fname, 'tex'))
              else:
                  full_fname = fname
              paths.append(full_fname)
          return paths
docs: Find all tex documents input by this root document.
  
          Returns
          -------
          paths : list
              List of filepaths for input documents. Paths are relative
              to the document (i.e., as written in the latex document).