What does it mean ?

This is the example code of the QR code. But I have some question about the this code.
What is the code mean in this line

 for code in img.find_qrcodes():

And what is the behind of the find_qrcodes() function. How can I find the explanation about the some function.

# QRCode Example
#
# This example shows the power of the OpenMV Cam to detect QR Codes
# using lens correction (see the qrcodes_with_lens_corr.py script for higher performance).

import sensor, image, time

sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QVGA)
sensor.skip_frames(time = 2000)
sensor.set_auto_gain(False) # must turn this off to prevent image washout...
clock = time.clock()

while(True):
    clock.tick()
    img = sensor.snapshot()
    img.lens_corr(1.8) # strength of 1.8 is good for the 2.8mm lens.
    for code in img.find_qrcodes():
        img.draw_rectangle(code.rect(), color = (255, 0, 0))
        print(code)
    print(clock.fps())

Hi, the method finds QR Codes. The C code that implements it is here:

https://github.com/openmv/openmv/blob/master/src/omv/img/qrcode.c