returns a Mapping of operation names and it's associated types.
        E.g. {'myQuery': 'query', 'myMutation': 'mutation'}

def operations_map(self):
        # type: () -> Dict[Union[str, None], str]
        """
        returns a Mapping of operation names and it's associated types.
        E.g. {'myQuery': 'query', 'myMutation': 'mutation'}
        """
        document_ast = self.document_ast
        operations = {}  # type: Dict[Union[str, None], str]
        for definition in document_ast.definitions:
            if isinstance(definition, ast.OperationDefinition):
                if definition.name:
                    operations[definition.name.value] = definition.operation
                else:
                    operations[None] = definition.operation

        return operations