docs: def col_rename(df,col_name,new_col_name):
      """ Changes a column name in a DataFrame
      Parameters:
      df - DataFrame
          DataFrame to operate on
      col_name - string
          Name of column to change
      new_col_name - string
          New name of column
      """
      col_list = list(df.columns)
      for index,value in enumerate(col_list):
          if value == col_name:
              col_list[index] = new_col_name
              break
      df.columns = col_list