code: def addValueToField(self, i, value=None):
      
  
      assert(len(self.fields)>i)
      if value is None:
        value = self.fields[i].dataClass.getNext()
        self.fields[i].addValue(value)
        return value
  
      else: self.fields[i].addValue(value)
docs: Add 'value' to the field i.
      Parameters:
      --------------------------------------------------------------------
      value:       value to be added
      i:           value is added to field i