[python-package] [docs] Expand class docs for Dataset (microsoft#6558)

R-package/DESCRIPTION

@@ -63,4 +63,4 @@ Imports:
     utils
 SystemRequirements:
     ~~CXXSTD~~
-RoxygenNote: 7.3.1
+RoxygenNote: 7.3.2

R-package/R/lgb.Dataset.R

@@ -758,8 +758,13 @@ Dataset <- R6::R6Class(
 )
 
 #' @title Construct \code{lgb.Dataset} object
-#' @description Construct \code{lgb.Dataset} object from dense matrix, sparse matrix
-#'              or local file (that was created previously by saving an \code{lgb.Dataset}).
+#' @description LightGBM does not train on raw data.
+#'              It discretizes continuous features into histogram bins, tries to
+#'              combine categorical features, and automatically handles missing and
+#               infinite values.
+#'
+#'              The \code{Dataset} class handles that preprocessing, and holds that
+#'              alternative representation of the input data.
 #' @inheritParams lgb_shared_dataset_params
 #' @param data a \code{matrix} object, a \code{dgCMatrix} object,
 #'             a character representing a path to a text file (CSV, TSV, or LibSVM),

docs/env.yml

@@ -12,7 +12,7 @@ dependencies:
   - r-markdown=1.12
   - r-matrix=1.6_4
   - r-pkgdown=2.0.7
-  - r-roxygen2=7.3.1
+  - r-roxygen2=7.3.2
   - scikit-learn>=1.4.0
   - sphinx>=6.0
   - sphinx_rtd_theme>=2.0

python-package/lightgbm/basic.py

@@ -1745,7 +1745,15 @@ def current_iteration(self) -> int:
 
 
 class Dataset:
-    """Dataset in LightGBM."""
+    """
+    Dataset in LightGBM.
+
+    LightGBM does not train on raw data.
+    It discretizes continuous features into histogram bins, tries to combine categorical features,
+    and automatically handles missing and infinite values.
+
+    This class handles that preprocessing, and holds that alternative representation of the input data.
+    """
 
     def __init__(
         self,