IndentationError: expected an indented block after 'with' statement on line 12

This error occurs when you are using the "with" statement in Python, but you have not properly indented the block of code that follows it. The "with" statement is used for working with context managers, which are objects that define how to enter and exit a context.

To resolve this error, you need to make sure that the block of code following the "with" statement is properly indented. Here is an example:

with open('file.txt', 'r') as f:
    for line in f:
        print(line)

In this example, the block of code that follows the "with" statement is indented with four spaces. This is the standard indentation in Python. You should make sure that your code follows this convention to avoid the "IndentationError" in the future.