Initializes parameters.

        Parameters
        ----------
        initializer : Initializer
        arg_params : dict
            Defaults to ``None``. Existing parameters. This has higher priority
            than `initializer`.
        aux_params : dict
            Defaults to ``None``. Existing auxiliary states. This has higher priority
            than `initializer`.
        allow_missing : bool
            Allow missing values in `arg_params` and `aux_params` (if not ``None``).
            In this case, missing values will be filled with `initializer`.
        force_init : bool
            Defaults to ``False``.
        allow_extra : boolean, optional
            Whether allow extra parameters that are not needed by symbol.
            If this is True, no error will be thrown when arg_params or aux_params
            contain extra parameters that is not needed by the executor.

def init_params(self, initializer=Uniform(0.01), arg_params=None, aux_params=None,
                    allow_missing=False, force_init=False, allow_extra=False):
        """Initializes parameters.

        Parameters
        ----------
        initializer : Initializer
        arg_params : dict
            Defaults to ``None``. Existing parameters. This has higher priority
            than `initializer`.
        aux_params : dict
            Defaults to ``None``. Existing auxiliary states. This has higher priority
            than `initializer`.
        allow_missing : bool
            Allow missing values in `arg_params` and `aux_params` (if not ``None``).
            In this case, missing values will be filled with `initializer`.
        force_init : bool
            Defaults to ``False``.
        allow_extra : boolean, optional
            Whether allow extra parameters that are not needed by symbol.
            If this is True, no error will be thrown when arg_params or aux_params
            contain extra parameters that is not needed by the executor.
        """
        if self.params_initialized and not force_init:
            return
        assert self.binded, 'call bind before initializing the parameters'
        self._curr_module.init_params(initializer=initializer, arg_params=arg_params,
                                      aux_params=aux_params, allow_missing=allow_missing,
                                      force_init=force_init, allow_extra=allow_extra)
        self._params_dirty = False
        self.params_initialized = True