code: def _add_field(self, field_type, name, value):
          
          try:
              self.__getattribute__(field_type).update({name: value})
          except:
              raise ValueError('Problem with field_type %s'  %field_type)
          #  Note that if process has attribute name, this will trigger The
          # setter method for that attribute
          self.__setattr__(name, value)
docs: Adds a new field to a specified dictionary. The field is also added
          as a process attribute. field_type can be 'input', 'diagnostics'