Save parameters to file.

        Parameters
        ----------
        filename : str
            Path to parameter file.
        strip_prefix : str, default ''
            Strip prefix from parameter names before saving.

def save(self, filename, strip_prefix=''):
        """Save parameters to file.

        Parameters
        ----------
        filename : str
            Path to parameter file.
        strip_prefix : str, default ''
            Strip prefix from parameter names before saving.
        """
        arg_dict = {}
        for param in self.values():
            weight = param._reduce()
            if not param.name.startswith(strip_prefix):
                raise ValueError(
                    "Prefix '%s' is to be striped before saving, but Parameter's "
                    "name '%s' does not start with '%s'. "
                    "this may be due to your Block shares parameters from other "
                    "Blocks or you forgot to use 'with name_scope()' when creating "
                    "child blocks. For more info on naming, please see "
                    "http://mxnet.incubator.apache.org/tutorials/basic/naming.html"%(
                        strip_prefix, param.name, strip_prefix))
            arg_dict[param.name[len(strip_prefix):]] = weight
        ndarray.save(filename, arg_dict)