Drive the robot forward by running both motors forward.

        :param float speed:
            Speed at which to drive the motors, as a value between 0 (stopped)
            and 1 (full speed). The default is 1.

        :param float curve_left:
            The amount to curve left while moving forwards, by driving the
            left motor at a slower speed. Maximum *curve_left* is 1, the
            default is 0 (no curve). This parameter can only be specified as a
            keyword parameter, and is mutually exclusive with *curve_right*.

        :param float curve_right:
            The amount to curve right while moving forwards, by driving the
            right motor at a slower speed. Maximum *curve_right* is 1, the
            default is 0 (no curve). This parameter can only be specified as a
            keyword parameter, and is mutually exclusive with *curve_left*.

def forward(self, speed=1, **kwargs):
        """
        Drive the robot forward by running both motors forward.

        :param float speed:
            Speed at which to drive the motors, as a value between 0 (stopped)
            and 1 (full speed). The default is 1.

        :param float curve_left:
            The amount to curve left while moving forwards, by driving the
            left motor at a slower speed. Maximum *curve_left* is 1, the
            default is 0 (no curve). This parameter can only be specified as a
            keyword parameter, and is mutually exclusive with *curve_right*.

        :param float curve_right:
            The amount to curve right while moving forwards, by driving the
            right motor at a slower speed. Maximum *curve_right* is 1, the
            default is 0 (no curve). This parameter can only be specified as a
            keyword parameter, and is mutually exclusive with *curve_left*.
        """
        curve_left = kwargs.pop('curve_left', 0)
        curve_right = kwargs.pop('curve_right', 0)
        if kwargs:
            raise TypeError('unexpected argument %s' % kwargs.popitem()[0])
        if not 0 <= curve_left <= 1:
            raise ValueError('curve_left must be between 0 and 1')
        if not 0 <= curve_right <= 1:
            raise ValueError('curve_right must be between 0 and 1')
        if curve_left != 0 and curve_right != 0:
            raise ValueError("curve_left and curve_right can't be used at "
                             "the same time")
        self.left_motor.forward(speed * (1 - curve_left))
        self.right_motor.forward(speed * (1 - curve_right))