import time
from xtendr.xtendrsystem import XtendRSystem

def my_callback():
    print("'example_plugin is finished pre-loading")
    
if __name__ == "__main__":
    """Example usage of the PluginSystem.
    
    Example:
    >>> system = XtendR()
    >>> system.attach("example_plugin")
    Attached plugin 'example_plugin'.
    >>> system.run("example_plugin")
    ExamplePlugin is running!
    >>> system.stop("example_plugin")
    ExamplePlugin has stopped!
    >>> system.detach("example_plugin")
    Detached plugin 'example_plugin'.
    """
    system = XtendRSystem()
    system.attach("example_plugin", my_callback)  # Assuming 'example_plugin/plugin_info.json' exists
    for i in range(3):
        print(f"Main program is running iteration {i+1}...")
        time.sleep(2)
    system.run("example_plugin", test="Hello!")
    system.stop("example_plugin")
    system.run("example_plugin", 25)
    system.stop("example_plugin")
    system.run("example_plugin", "Hello!", 25)
    system.stop("example_plugin")
    system.detach("example_plugin")