def _set_available_styles(self):
        """Set the internal styles list and available options in a structure as following:

            param: javadoc: name = '@param'
                            sep  = ':'
                   reST:    name = ':param'
                            sep  = ':'
                   ...
            type:  javadoc: name = '@type'
                            sep  = ':'
                   ...
            ...

        And sets the internal groups style:
            param:  'params', 'args', 'parameters', 'arguments'
            return: 'returns', 'return'
            raise:  'raises', 'raise', 'exceptions', 'exception'

        """
        options_tagstyle = {'keys': ['param', 'type', 'returns', 'return', 'rtype', 'raise'],
                            'styles': {'javadoc': ('@', ':'),  # tuple:  key prefix, separator
                                       'reST': (':', ':'),
                                       'cstyle': ('\\', ' ')}
                           }
        self.tagstyles = list(options_tagstyle['styles'].keys())
        for op in options_tagstyle['keys']:
            self.opt[op] = {}
            for style in options_tagstyle['styles']:
                self.opt[op][style] = {'name': options_tagstyle['styles'][style][0] + op,
                                       'sep': options_tagstyle['styles'][style][1]
                                      }
        self.opt['return']['reST']['name'] = ':returns'
        self.opt['raise']['reST']['name'] = ':raises'
        self.groups = {
                    'param': ['params', 'args', 'parameters', 'arguments'],
                    'return': ['returns', 'return'],
                    'raise': ['raises', 'exceptions', 'raise', 'exception']
                    }
Set the internal styles list and available options in a structure as following:

            param: javadoc: name = '@param'
                            sep  = ':'
                   reST:    name = ':param'
                            sep  = ':'
                   ...
            type:  javadoc: name = '@type'
                            sep  = ':'
                   ...
            ...

        And sets the internal groups style:
            param:  'params', 'args', 'parameters', 'arguments'
            return: 'returns', 'return'
            raise:  'raises', 'raise', 'exceptions', 'exception'