def add_parameter(self, field_name, param_name, param_value):
try:<EOL><INDENT>self.fields[field_name]['<STR_LIT>'][param_name] = param_value<EOL><DEDENT>except Exception as ex:<EOL><INDENT>raise ScriptFieldsError("<STR_LIT>" % (param_name, param_value, ex))<EOL><DEDENT>return self<EOL>
Add a parameter to a field into script_fields

The ScriptFields object will be returned, so calls to this can be chained.