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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 preprocess_cell( self, cell: "NotebookNode", resources: dict, index: int ) -> Tuple["NotebookNode", dict]: """Preprocess cell. Parameters cell : NotebookNode cell Notebook cell being processed resources : dictionary Additional resources used in the conversion process. Allows preprocessors to pass variables into the Jinja engine. cell_index : int Index of the cell being processed (see base.py) """

        if cell.cell_type == "markdown":
            variables = cell["metadata"].get("variables", {})
            if len(variables) > 0:
                cell.source = self.replace_variables(cell.source, variables)
                if resources.get("delete_pymarkdown", False):
                    del cell.metadata["variables"]
        return cell, resources