df.groupBy { city }.values()

Input DataFrame: rowsCount = 7, columnsCount = 5

Step 1: GroupBy

Output DataFrame: rowsCount = 6, columnsCount = 5

df.groupBy { city }.values { name and age }

Input DataFrame: rowsCount = 7, columnsCount = 5

Step 1: GroupBy

Output DataFrame: rowsCount = 6, columnsCount = 3

df.groupBy { city }.values { weight into "weights" }

Input DataFrame: rowsCount = 7, columnsCount = 5

Step 1: GroupBy

Output DataFrame: rowsCount = 6, columnsCount = 2