def _add_field(self, field_type, name, value):
try:<EOL><INDENT>self.__getattribute__(field_type).update({name: value})<EOL><DEDENT>except:<EOL><INDENT>raise ValueError('<STR_LIT>'  %field_type)<EOL><DEDENT>self.__setattr__(name, value)<EOL>
Adds a new field to a specified dictionary. The field is also added
        as a process attribute. field_type can be 'input', 'diagnostics