## Metric

Makes a two-tensor a metric.

Labels the object as a symmetric tensor, and optionally gives it the
indicated signature through the `signature`parameter.

g_{m n}::Metric(signature=1).
ex:= g_{m n} A^{n p};
eliminate_metric(_);

\(\displaystyle{}g_{m n} A^{n p}\)

{\color{red}{

Traceback (most recent call last): File "<string>", line 3, in <module> NameError: name 'eliminate_metric' is not defined}}

Objects declared as

`Metric`

can be used to automatically
raise or lower indices using the
`eliminate_metric`

algorithm, as above.