<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def validate_message_dict(self, request_body):
 """With the JSON dict that will be sent to SendGrid's API, check the content for SendGrid API keys - throw exception if found. :param request_body: The JSON dict that will be sent to SendGrid's API. :type request_body: JSON serializable structure :raise ApiKeyIncludedException: If any content in request_body matches regex """


        # Handle string in edge-case
        if isinstance(request_body, str):
            self.validate_message_text(request_body)

        # Default param
        elif isinstance(request_body, dict):

            contents = request_body.get("content", list())

            for content in contents:
                if content is not None:
                    if (content.get("type") == "text/html" or
                            isinstance(content.get("value"), str)):
                        message_text = content.get("value", "")
                        self.validate_message_text(message_text)