Operator(+) overloading for PyObject

I port my following Python code into using PyPlot:
```julia
import PyPlot

const plt = PyPlot

fig, ax = plt.subplots(facecolor="w", edgecolor="k")

t = 1:24
x = 1:24
y= 24:-1:1
ax.plot(t,x, label="x")
ax2 = ax.twinx()
ax2.plot(t,y, label="y")

lines, labels = ax.get_legend_handles_labels()
lines2, labels2 = ax2.get_legend_handles_labels()
ax.legend(lines + lines2, labels + labels2, loc="upper left", fontsize=20, ncol = 1)

fig.tight_layout()
plt.show()
```

In `lines + lines2`, I encounter an error:
```
PyError ($(Expr(:escape, :(ccall(#= C:\Users\meta\.julia\packages\PyCall\BcTLp\src\pyoperators.jl:12 =# @pysym(:PyNumber_Add), PyPtr, (PyPtr, PyPtr), a, b)))))
TypeError("unsupported operand type(s) for +: 'Line2D' and 'Line2D'")

Stacktrace:
[1] pyerr_check at C:\Users\meta\.julia\packages\PyCall\BcTLp\src\exception.jl:62 [inlined]
[2] pyerr_check at C:\Users\meta\.julia\packages\PyCall\BcTLp\src\exception.jl:66 [inlined]
[3] _handle_error(::String) at C:\Users\meta\.julia\packages\PyCall\BcTLp\src\exception.jl:83
[4] macro expansion at C:\Users\meta\.julia\packages\PyCall\BcTLp\src\exception.jl:97 [inlined]
[5] + at C:\Users\meta\.julia\packages\PyCall\BcTLp\src\pyoperators.jl:11 [inlined]
[6] _broadcast_getindex_evalf at .\broadcast.jl:648 [inlined]
[7] _broadcast_getindex at .\broadcast.jl:621 [inlined]
[8] getindex at .\broadcast.jl:575 [inlined]
[9] macro expansion at .\broadcast.jl:932 [inlined]
[10] macro expansion at .\simdloop.jl:77 [inlined]
[11] copyto! at .\broadcast.jl:931 [inlined]
[12] copyto! at .\broadcast.jl:886 [inlined]
[13] copy at .\broadcast.jl:862 [inlined]
[14] materialize at .\broadcast.jl:837 [inlined]
[15] broadcast_preserving_zero_d at .\broadcast.jl:826 [inlined]
[16] +(::Array{PyObject,1}, ::Array{PyObject,1}) at .\arraymath.jl:47
[17] top-level scope at In[177]:17
[18] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091
[19] execute_code(::String, ::String) at C:\Users\meta\.julia\packages\IJulia\rWZ9e\src\execute_request.jl:27
[20] execute_request(::ZMQ.Socket, ::IJulia.Msg) at C:\Users\meta\.julia\packages\IJulia\rWZ9e\src\execute_request.jl:86
[21] #invokelatest#1 at .\essentials.jl:710 [inlined]
[22] invokelatest at .\essentials.jl:709 [inlined]
[23] eventloop(::ZMQ.Socket) at C:\Users\meta\.julia\packages\IJulia\rWZ9e\src\eventloop.jl:8
[24] (::IJulia.var"#15#18")() at .\task.jl:356
```

It seems that operator `+` is not appropriately overloaded for PyObject.
I wonder that how to tackle this issue.

Reproduce el caso reportado de lines + lines2 y, después, inspecciona src/pyoperators.jl:11 y la ruta de arrays/broadcast de Julia mostrada en el stack trace. Determina la semántica prevista para combinar estos arrays de PyObject y define la finalización haciendo que la operación se comporte de forma coherente con esa intención, con cobertura de regresión si la estructura de pruebas del proyecto identifica un lugar adecuado.

Escrito por el modelo de indexación a partir del texto del issue.