1 | initial version |

here is a solution using fast_callable:

```
sage: (x, y, z) = var('x, y, z')
sage: assume(x, 'real', y, 'real')
sage: from sage.ext.fast_callable import fast_callable
sage: cabs = fast_callable(sqrt(real(z)^2 + imag(z)^2), vars=[z])
sage: cg = fast_callable(diff(100*cabs(x/(245*x^4/(20*x^2 - I*x*(20*y + 1) - 20) - 100*x^2 + I*x + 100)), x), vars=[x, y])
sage: region_plot(cg(x, y) < 0, (x, 0.7, 1.7), (y, 0, 1), plot_points=100)
```

it seems to work and in a reasonable time, but someone more knowledgeable may have a better approach!

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