code: def drop_constant_columns(df: pd.DataFrame) -> pd.DataFrame:
      """Finds and drops the constant columns from a Pandas DataFrame.
  
      Examples:
          >>> import pandas as pd
          >>> import janitor
          >>> data_dict = {
          ...     "a": [1, 1, 1],
          ...     "b": [1, 2, 3],
          ...     "c": [1, 1, 1],
          ...     "d": ["rabbit", "leopard", "lion"],
          ...     "e": ["Cambridge", "Shanghai", "Basel"]
          ... }
          >>> df = pd.DataFrame(data_dict)
          >>> df
             a  b  c        d          e
          0  1  1  1   rabbit  Cambridge
          1  1  2  1  leopard   Shanghai
          2  1  3  1     lion      Basel
          >>> df.drop_constant_columns()
             b        d          e
          0  1   rabbit  Cambridge
          1  2  leopard   Shanghai
          2  3     lion      Basel
  
      Args:
          df: Input Pandas DataFrame
  
      Returns:
          The Pandas DataFrame with the constant columns dropped.
      """
      return df.loc[:, df.nunique().ne(1)]
  
label_desc: Use image node_id 1 for calling a global function with example usage: drop_constant_columns(df) and returns: df