docs: def add_ignore(self):
          """ Writes a .gitignore file to ignore the generated data file. """
          path = self.lazy_folder + self.ignore_filename
          
          # If the file exists, return.
          if os.path.isfile(os.path.realpath(path)):
              return None
  
          sp, sf = os.path.split(self.data_file)
  
          #Write the file.
          try:
              handle = open(path,'w')
              handle.write(sf + '\n')
          except IOError as e:
              raise e
  
          # Close the handle and return.
          handle.close()
          return None