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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 build_y(self):
 """Build transmission line admittance matrix into self.Y"""

        if not self.n:
            return
        self.y1 = mul(self.u, self.g1 + self.b1 * 1j)
        self.y2 = mul(self.u, self.g2 + self.b2 * 1j)
        self.y12 = div(self.u, self.r + self.x * 1j)
        self.m = polar(self.tap, self.phi * deg2rad)
        self.m2 = abs(self.m)**2
        self.mconj = conj(self.m)

        # build self and mutual admittances into Y
        self.Y = spmatrix(
            div(self.y12 + self.y1, self.m2), self.a1, self.a1,
            (self.nb, self.nb), 'z')
        self.Y -= spmatrix(
            div(self.y12, self.mconj), self.a1, self.a2, (self.nb, self.nb),
            'z')
        self.Y -= spmatrix(
            div(self.y12, self.m), self.a2, self.a1, (self.nb, self.nb), 'z')
        self.Y += spmatrix(self.y12 + self.y2, self.a2, self.a2,
                           (self.nb, self.nb), 'z')