CS50 SHENANIGANS (error message that i dont understand)

Question

i was taking GD50 (cs50 game dev course) lecture 1 (flappy bird) and i encountered this error: Error

Bird.lua:19: attempt to index field 'wasPressed' (a function value)

bird = Class{}

local GRAVITY = 19.5

function bird:init()
    self.image = love.graphics.newImage('bird.png')
    self.width = self.image:getWidth()
    self.height = self.image:getHeight()

    self.x = VIRTUAL_WIDTH / 2 - (self.width / 2)
    self.y = VIRTUAL_HEIGHT / 2 - (self.height / 2)

    self.dy = 0
end

function bird:update(dt)
    self.dy = self.dy + GRAVITY * dt

    if love.keyboard.wasPressed['space'] then
        self.dy = -5
    end

    self.y = self.y + self.dy
end

function bird:render()
    love.graphics.draw(self.image, self.x, self.y)
end