Private method.  Don't use directly.

def _bind(self, args, kwargs, partial=False):
        """Private method.  Don't use directly."""

        arguments = OrderedDict()

        parameters = iter(self.parameters.values())
        parameters_ex = ()
        arg_vals = iter(args)

        if partial:
            # Support for binding arguments to 'functools.partial' objects.
            # See 'functools.partial' case in 'signature()' implementation
            # for details.
            for param_name, param in self.parameters.items():
                if param._partial_kwarg and param_name not in kwargs:
                    # Simulating 'functools.partial' behavior
                    kwargs[param_name] = param.default

        while True:
            # Let's iterate through the positional arguments and corresponding
            # parameters
            try:
                arg_val = next(arg_vals)
            except StopIteration:
                # No more positional arguments
                try:
                    param = next(parameters)
                except StopIteration:
                    # No more parameters. That's it. Just need to check that
                    # we have no `kwargs` after this while loop
                    break
                else:
                    if param.kind == _VAR_POSITIONAL:
                        # That's OK, just empty *args.  Let's start parsing
                        # kwargs
                        break
                    elif param.name in kwargs:
                        if param.kind == _POSITIONAL_ONLY:
                            msg = (
                                "{arg!r} parameter is positional only, "
                                "but was passed as a keyword"
                            )
                            msg = msg.format(arg=param.name)
                            raise TypeError(msg)
                        parameters_ex = (param,)
                        break
                    elif param.kind == _VAR_KEYWORD or param.default is not _empty:
                        # That's fine too - we have a default value for this
                        # parameter.  So, lets start parsing `kwargs`, starting
                        # with the current parameter
                        parameters_ex = (param,)
                        break
                    else:
                        if partial:
                            parameters_ex = (param,)
                            break
                        else:
                            msg = "{arg!r} parameter lacking default value"
                            msg = msg.format(arg=param.name)
                            raise TypeError(msg)
            else:
                # We have a positional argument to process
                try:
                    param = next(parameters)
                except StopIteration:
                    raise TypeError("too many positional arguments")
                else:
                    if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY):
                        # Looks like we have no parameter for this positional
                        # argument
                        raise TypeError("too many positional arguments")

                    if param.kind == _VAR_POSITIONAL:
                        # We have an '*args'-like argument, let's fill it with
                        # all positional arguments we have left and move on to
                        # the next phase
                        values = [arg_val]
                        values.extend(arg_vals)
                        arguments[param.name] = tuple(values)
                        break

                    if param.name in kwargs:
                        raise TypeError(
                            "multiple values for argument "
                            "{arg!r}".format(arg=param.name)
                        )

                    arguments[param.name] = arg_val

        # Now, we iterate through the remaining parameters to process
        # keyword arguments
        kwargs_param = None
        for param in itertools.chain(parameters_ex, parameters):
            if param.kind == _POSITIONAL_ONLY:
                # This should never happen in case of a properly built
                # Signature object (but let's have this check here
                # to ensure correct behaviour just in case)
                raise TypeError(
                    "{arg!r} parameter is positional only, "
                    "but was passed as a keyword".format(arg=param.name)
                )

            if param.kind == _VAR_KEYWORD:
                # Memorize that we have a '**kwargs'-like parameter
                kwargs_param = param
                continue

            param_name = param.name
            try:
                arg_val = kwargs.pop(param_name)
            except KeyError:
                # We have no value for this parameter.  It's fine though,
                # if it has a default value, or it is an '*args'-like
                # parameter, left alone by the processing of positional
                # arguments.
                if (
                    not partial
                    and param.kind != _VAR_POSITIONAL
                    and param.default is _empty
                ):
                    raise TypeError(
                        "{arg!r} parameter lacking default value".format(arg=param_name)
                    )

            else:
                arguments[param_name] = arg_val

        if kwargs:
            if kwargs_param is not None:
                # Process our '**kwargs'-like parameter
                arguments[kwargs_param.name] = kwargs
            else:
                raise TypeError("too many keyword arguments")

        return self._bound_arguments_cls(self, arguments)