UnboundLocalError: local variable 'arr_chest' referenced before assignment

This error occurs when you try to access or modify a local variable before it has been assigned a value. In Python, variables must be assigned a value before they can be used.

For example, consider the following code:

def my_function():
    print(arr_chest)
    arr_chest = ['item1', 'item2', 'item3']
    
my_function()

In this code, we are trying to print the value of `arr_chest` before it has been assigned a value. This will result in the `UnboundLocalError` error.

To fix this error, you need to make sure that the variable has been assigned a value before it is accessed or modified. You can do this by initializing the variable with a default value or assigning a value to it before it is used in your code.