AttributeError: 'NoneType' object has no attribute 'fileno'

This error occurs when you try to call the `fileno()` method on a `NoneType` object. The `fileno()` method is used to get the file descriptor of a file-like object, and it can only be called on objects that have a file descriptor. In this case, the object is `None`, which means that it does not have a file descriptor and therefore cannot have the `fileno()` method called on it.

To fix this error, you need to make sure that the object you are calling the `fileno()` method on is not `None`. You can check for this by adding an `if` statement before calling the method:

if my_object is not None:
    my_object.fileno()
else:
    # handle the case where my_object is None