Return the mean and the covariance matrix of the conditional distribution of a linear Gaussian SCM
analytic_linear_gaussian_conditining(scm, situation)A linear Gaussian SCM
A list with the following element:
condition : either a string that gives an SQL query ( e.g. "select x,y,z from DATA where" ) or a data.table consisting of the valid rows ( e.g. data.table::data.table( x = 0, y = 0))