DOC: add value counts as related method to count (pandas-dev#37209)

Author: erictleung

pandas/core/frame.py

@@ -8547,6 +8547,7 @@ def count(self, axis=0, level=None, numeric_only=False):
         See Also
         --------
         Series.count: Number of non-NA elements in a Series.
+        DataFrame.value_counts: Count unique combinations of columns.
         DataFrame.shape: Number of DataFrame rows and columns (including NA
             elements).
         DataFrame.isna: Boolean same-sized DataFrame showing places of NA