How to use the pymoca.ast.Expression function in pymoca

src_left = self.get_mx(tree.left)

        if isinstance(tree.right, list):
            src_right = ca.vertcat(*[self.get_mx(c) for c in tree.right])
        else:
            src_right = self.get_mx(tree.right)

        src_left = ca.MX(src_left)
        src_right = ca.MX(src_right)

        # According to the Modelica spec,
        # "It is possible to omit left hand side component references and/or truncate the left hand side list in order to discard outputs from a function call."
        if isinstance(tree.right, ast.Expression) and tree.right.operator in self.root.classes:
            if src_left.size1() < src_right.size1():
                src_right = src_right[0:src_left.size1()]
        if isinstance(tree.left, ast.Expression) and tree.left.operator in self.root.classes:
            if src_left.size1() > src_right.size1():
                src_left = src_left[0:src_right.size1()]

        # If dimensions between the lhs and rhs do not match, but the dimensions of lhs
        # and transposed rhs do match, transpose the rhs.
        if src_left.shape != src_right.shape and src_left.shape == src_right.shape[::-1]:
            src_right = ca.transpose(src_right)

        self.src[tree] = src_left - src_right