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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 checkSquareStochastic(matrix):
 """Check if ``matrix`` is a square and row-stochastic. To pass the check the following conditions must be met: * The matrix should be square, so the number of columns equals the number of rows. * The matrix should be row-stochastic so the rows should sum to one. * Each value in the matrix must be positive. If the check does not pass then a mdptoolbox.util.Invalid Arguments --------- ``matrix`` : numpy.ndarray, scipy.sparse.*_matrix A two dimensional array (matrix). Notes ----- Returns None if no error has been detected, else it raises an error. """

    if not isSquare(matrix):
        raise _error.SquareError
    if not isStochastic(matrix):
        raise _error.StochasticError
    if not isNonNegative(matrix):
        raise _error.NonNegativeError