code: def default_value(fieldname, datatype):
      
      if fieldname in tsdb_coded_attributes:
          return str(tsdb_coded_attributes[fieldname])
      else:
          return _default_datatype_values.get(datatype, '')
docs: Return the default value for a column.
  
      If the column name (e.g. *i-wf*) is defined to have an idiosyncratic
      value, that value is returned. Otherwise the default value for the
      column's datatype is returned.
  
      Args:
          fieldname: the column name (e.g. `i-wf`)
          datatype: the datatype of the column (e.g. `:integer`)
      Returns:
          The default value for the column.
  
      .. deprecated:: v0.7.0