1 | initial version |

Depending on what you want to do, you can maybe also consider using the constructor `TateAlgebra`

(it is not exactly the same than power series but much effort is done to handle precision correctly):

```
sage: K.<u> = Qq(3^2)
sage: L.<pi> = K.extension(x^2 - 3)
sage: L
3-adic Eisenstein Extension Field in pi defined by x^2 - 3 over its base field
sage: A.<x> = TateAlgebra(L)
sage: (1 - pi*x).inverse_of_unit()
(1 + O(pi^40)) + (pi + O(pi^40))*x + ... + O(pi^40 * <x>)
```

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