def column_names sheet
    
      names = []
      
      titles = sheet.column_titles
      
      sheet.each_cell_definition do |column, i|
      
        if titles[i]

          names << titles[i]
          
        elsif column.respond_to?(:value_name)
          
          names << column.value_name
          
        else
          
          names << nil
          
        end
        
      end
      
      names
      
    end
def column_names sheet
    
      names = []
      
      titles = sheet.column_titles
      
      sheet.each_cell_definition do |column, i|
      
        if titles[i]

          names << titles[i]
          
        elsif column.respond_to?(:value_name)
          
          names << column.value_name
          
        else
          
          names << nil
          
        end
        
      end
      
      names
      
    end
returns an array of column title names, variable names or nil(s)