class_docstr: Convert a pandas DataFrame to a suitable VW format.
  Instances of this class are built with classes such as SimpleLabel,
  MulticlassLabel, Feature or Namespace.
  
  The class also provided a convenience constructor to initialize the class
  based on the target/features column names only.
class_docstr_tok: ["Convert","a","pandas","DataFrame","to","a","suitable","VW","format",".","Instances","of","this","class","are","built","with","classes","such","as","SimpleLabel",",","MulticlassLabel",",","Feature","or","Namespace",".","The","class","also","provided","a","convenience","constructor","to","initialize","the","class","based","on","the","target\/features","column","names","only","."]
docstr: Create an empty string column.
  
  Returns:
      A column of empty string with as much rows as the input dataframe.
docstr_tok: ["Create","an","empty","string","column",".","Returns",":","A","column","of","empty","string","with","as","much","rows","as","the","input","dataframe","."]
code: def empty_col(self) -> pd.Series:
      """Create an empty string column.
  
      Returns:
          A column of empty string with as much rows as the input dataframe.
      """
      return pd.Series(data=[""] * self.n_rows, index=self.df.index)
  
imports: import warnings
  import numpy
  import pandas
  from typing import Any, Hashable, List, Optional, Tuple, Type, Union
label_desc: Use image node_id 13 for calling the DFtoVW obj's underlying member method code with example usage: obj.empty_col() and returns: pd