class arguements

[buran]

lines 3-9 is the __init__() functions. That is one of the number of special methods, so called dunders (from double underscore) functions that can be used to customize class.
__init__() is called at time of class instantiation (i.e. every time when you create an instance of the class).
on lines 4-9 they initialize some class attributes. Note that although normally you would inirialize some if not all attributes in __init__(), it's not mandatory that all attributes are initializaed in __init__(). actually it's not mandatory to have __init__()