Constructing a wtforms\' TextAreaField is something like this:
content = wtf.TextAreaField(\'Content\', id=\"content-area\", validators=[validators.Required()])
You are not supposed to do it in the place where you declare the widget. You have do it in the template. For eg:
{{form.content(rows='50',cols='100')}}
Need to ensure the rows and cols are specified as a string.