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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 build_pages(self):
 """Iterate over the pages_dir and build the pages """

        for root, _, files in os.walk(self.pages_dir):
            base_dir = root.replace(self.pages_dir, "").lstrip("/")
            if not base_dir.startswith("_"):
                for f in files:
                    src_file = os.path.join(base_dir, f)
                    self._build_page(src_file)