rewrite.py 文件源码

def push_format_context(self):
        """Create a new formatting context.

        The format context is used for when an explanation wants to
        have a variable value formatted in the assertion message.  In
        this case the value required can be added using
        .explanation_param().  Finally .pop_format_context() is used
        to format a string of %-formatted values as added by
        .explanation_param().

        """
        self.explanation_specifiers = {}
        self.stack.append(self.explanation_specifiers)