# retrieve field of a Matrix

it may sound a stupid question,

but I'd like to know how to retrieve in a variable the field overwhich a Matrix is defined

for example, if

```
K=GF(7)
M=random_matrix(K,2,2)
```

Is there a function where i can define for example
`K'= M.field()`

[and K' would be equal to K]

?

M.parent() provides some information of course, but we cannot use it directly