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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_plugin(self, f):
 """Adding and verifying plugin. Args: f: the filepath for the plugin. """

        if f.endswith('.py'):

            # Just the basename without extension
            plugin_name = os.path.splitext(os.path.basename(f))[0]

            # It's possible the plugin has been modified and needs to be reloaded
            if plugin_name in sys.modules:
                try:
                    handler = reload(sys.modules[plugin_name])
                    print'\t- %s %sRELOAD%s' % (plugin_name, color.Yellow, color.Normal)
                except ImportError, error:
                    print 'Failed to import plugin: %s (%s)' % (plugin_name, error)
                    return
            else:
                # Not already loaded so try to import it
                try:
                    handler = __import__(plugin_name, globals(), locals(), [], -1)
                except ImportError, error:
                    print 'Failed to import plugin: %s (%s)' % (plugin_name, error)
                    return

            # Run the handler through plugin validation
            plugin = self.validate(handler)
            print '\t- %s %sOK%s' % (plugin_name, color.Green, color.Normal)
            if plugin:

                # Okay must be successfully loaded so capture the plugin meta-data,
                # modification time and register the plugin through the callback
                plugin['name'] = plugin_name
                plugin['dependencies'] = plugin['class'].dependencies
                plugin['docstring'] = plugin['class'].__doc__
                plugin['mod_time'] = datetime.utcfromtimestamp(os.path.getmtime(f))

                # Plugin may accept sample_sets as input
                try:
                    plugin['sample_set_input'] = getattr(plugin['class'], 'sample_set_input')
                except AttributeError:
                    plugin['sample_set_input'] = False

                # Now pass the plugin back to workbench
                self.plugin_callback(plugin)