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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_directed_unweighted(user):
 """ Returns a directed, unweighted matrix where an edge exists if there is at least one call or text. """

    matrix = _interaction_matrix(user, interaction=None)
    for a in range(len(matrix)):
        for b in range(len(matrix)):
            if matrix[a][b] is not None and matrix[a][b] > 0:
                matrix[a][b] = 1

    return matrix