title: Create drop down with sheet elements in XlsxWriter
body: <p>So I'm creating a spreadsheet with certain data. Some cells in the spreadsheet need to have a drop down list with pre-defined data. For some cells the process has been pretty straightforward:</p>
  
  <pre><code>worksheet.data_validation(start_row, start_column, end_row, end_column, {'validate': 'list', 'source': options }
  </code></pre>
  
  <p>where options is a list of items.</p>
  
  <p>It turns out that this list of items is converted to a string, if the string has more than 255 characters then (due to excel limitations) is not possible to created the drop down.</p>
  
  <p>Since different cells may have different options, I'm checking if the length of options (converted to string) is >= 255, if so then I'm creating a new sheet and writing down the options there.</p>
  
  <pre><code>def create_options_sheet(self, name, values):
  
      options_worksheet = self.workbook.add_worksheet(name)
  
      opt_col = 0
      opt_row = 0
  
      for elem in values:
          options_worksheet.write(opt_row, opt_col, elem)
          opt_row += 1
  </code></pre>
  
  <p>So I'm planning to access these options from the current sheet taking an approach similar to this:</p>
  
  <pre><code>current_worksheet.data_validation(start_row, start_column, end_row, end_column, {'validate': 'list', 'source': options_sheet})
  </code></pre>
  
  <p>Where options_sheet would be a reference to the options sheet using a range like =$A$1:$A$10. My question is: how can I load that sheet and access it from my current sheet?</p>