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+from csympy import Symbol, sin, cos, sqrt, Add, function_symbol%0A%0Adef test_sin():%0A    x = Symbol(%22x%22)%0A    y = Symbol(%22y%22)%0A    e = sin(x)%0A    assert e.subs(%7Bx: y%7D) == sin(y)%0A    assert e.subs(%7Bx: y%7D) != sin(x)%0A

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