check is a generic S3 method for S3 classes inheriting
from item. It is a logical method checking if the item is well defined
with respect to a risk (i.e. that all information necessary for valuating
the item is available).
# S3 method for liability
check(object, market.risk, ...)S3 object of class liability.
S3 object of class marketRisk created using the constructor
marketRisk.
additional arguments.
a logical value, is the liability consistent with the marketRisk?