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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 matrix_str(p, decimal_places=2, print_zero=True, label_columns=False):
    '''Pretty-print the matrix.'''
    return '[{0}]'.format("\n  ".join([(str(i) if label_columns else '') + vector_str(a, decimal_places, print_zero) for i, a in enumerate(p)]))