code: def set_os_eol_chars(self, index=None, osname=None):
          
          if osname is None:
              osname = os.name
          if index is None:
              index = self.get_stack_index()
          finfo = self.data[index]
          eol_chars = sourcecode.get_eol_chars_from_os_name(osname)
          finfo.editor.set_eol_chars(eol_chars)
          finfo.editor.document().setModified(True)
docs: Sets the EOL character(s) based on the operating system.
  
          If `osname` is None, then the default line endings for the current
          operating system (`os.name` value) will be used.
  
          `osname` can be one of:
              ('posix', 'nt', 'java')