def apply_style(self, sheet_name, cell, cell_format_dict):
    """Apply style for any cell, with value or not. Overwrites cell with joined 
        cell_format_dict and existing format and with existing or blank value"""
written_cell_data = self.written_cells[sheet_name].get(cell)
if written_cell_data:
    existing_value, existing_cell_format_dict = self.written_cells[sheet_name][
        cell]
updated_format = dict(existing_cell_format_dict or {}, **cell_format_dict)
pandas: how to format cells after exporting to Excel