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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 _get_pdf_list(self, input_pdfs):
 """ Generate list of PDF documents. :param input_pdfs: List of PDFs or a directory path Directory - Scans directory contents List - Filters list to assert all list items are paths to PDF documents :return: List of PDF paths """

        if isinstance(input_pdfs, list):
            return [pdf for pdf in input_pdfs if self.validate(pdf)]
        elif os.path.isdir(input_pdfs):
            return [os.path.join(input_pdfs, pdf) for pdf in os.listdir(input_pdfs) if self.validate(pdf)]