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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_code_cell(cells, source):
 """Add a code cell containing `source` to the notebook."""

    from nbformat.v4.nbbase import new_code_cell
    n_code_cells = len([c for c in cells if c['cell_type'] == 'code'])
    cells.append(new_code_cell(source=source, execution_count=n_code_cells+1))