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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_const(features):
 """ Prepend the constant feature 1 as first feature and return the modified feature set. Parameters features : ndarray or DataFrame """

    content = np.empty((features.shape[0], features.shape[1] + 1), dtype='float64')
    content[:, 0] = 1.
    if isinstance(features, np.ndarray):
        content[:, 1:] = features
        return content
    content[:, 1:] = features.iloc[:, :].values
    cols = ['Constant'] + features.columns.tolist()
    return pd.DataFrame(data=content, index=features.index, columns=cols, dtype='float64')