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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_posts(self, path='posts'):
 		""" 		Look through a directory for markdown files and add them as posts. 		"""

		path = os.path.join(self.root_path, path)
		self.cm.add_posts([
			self.cm.Post.from_file(file)
			for file in _listfiles(path)
		])