Takes a base-learner and extracts information.
# S3 method for blg
extract(
  object,
  what = c("design", "penalty", "index"),
  asmatrix = FALSE,
  expand = FALSE,
  ...
)a base-learner
a character specifying the quantities to extract. This can be a subset of "design" (default; design matrix), "penalty" (penalty matrix) and "index" (index of ties used to expand the design matrix)
a logical indicating whether the the returned matrix should be 
coerced to a matrix (default) or if the returned object stays as it is 
(i.e., potentially a sparse matrix). This option is only applicable if extract 
returns matrices, i.e., what = "design" or what = "penalty".
a logical indicating whether the design matrix should be expanded 
(default: FALSE). This is useful if ties were taken into account either manually 
(via argument index in a base-learner) or automatically for data sets with many 
observations. expand = TRUE is equivalent to extract(B)[extract(B, what = "index"),] 
for a base-learner B.
currently not used
extract for the extract function 
of the package mboost.