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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 Mu(i, j, s, N, excluded_mu=[]):
 """This function calculates the global index mu for the element i, j. It returns the index for the real part if s=0 and the one for the imaginary part if s=1. """

    if i == j:
        if s == -1:
            if i == 1:
                return 0
            else:
                mes = 'There is no population rhoii with i='+str(i)+'.'
                raise ValueError(mes)
        mu = i-1
    elif i > j and s == 1:
        mu = i - j + sum([N-k for k in range(1, j)])+N-1
    elif i > j and s == -1:
        mu = i - j + sum([N-k for k in range(1, j)])+N-1 + N*(N-1)/2
    else:
        mes = 'i='+str(i)+', j='+str(j)
        mes += ' Equations for i<j are not calculated.'+str(s)
        raise ValueError(mes)

    if excluded_mu != []:
        mu = mu-len([ii for ii in excluded_mu if ii < mu])
    return mu