1 | initial version |

There are several little problems in your code.

First you do not need to use `SR`

in `build_variables`

(avoid `SR`

as much as possible when using polynomials). You can do

```
def build_variables(n):
names = []
for i in range(n):
for j in range(n):
names += ['x_' + str(i) + '_' + str(j)]
return(names)
```

Then in the `lambda_siep`

function, you should only use the result `my_variables`

of `build_variables`

once, inside the `PolynomialRing`

constructor.

Then you should not use `my_variables`

anymore, but instead your `X`

in the line

```
J[i,j] = derivative(Y[0][i], X[j][j])
```

The two lines

```
R.gens()
R.inject_variables()
```

are useless and can be removed. In particular, `inject_variables`

is only to be used in interactive mode.

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