Retrieve the list of variables that participate in an SOS constraint,
and the associated coefficients. The return value is the length of
this list. If you would like to allocate space for the result before
retrieving the result, call the method first with
arguments to determine the appropriate array lengths.
sos: The SOS set of interest.
vars: A list of variables that participate in sos.
weights: The SOS weights for each participating variable.
typeP: The type of the SOS set (either GRB_SOS_TYPE1 or GRB_SOS_TYPE2).
The length of the result arrays.