How to use the sendgrid.helpers.mail.Substitution function in sendgrid

to_emails = [
            To(email='test+to0@example.com',
                name='Example Name 0',
                substitutions=[
                    Substitution('-name-', 'Example Name Substitution 0'),
                    Substitution('-github-', 'https://example.com/test0'),
                ],
                subject=Subject('Override Global Subject')),
            To(email='test+to1@example.com',
                name='Example Name 1',
                substitutions=[
                    Substitution('-name-', 'Example Name Substitution 1'),
                    Substitution('-github-', 'https://example.com/test1'),
                ])
        ]
        global_substitutions = Substitution('-time-', '2019-01-01 00:00:00')
        message = Mail(
            from_email=From('test+from@example.com', 'Example From Name'),
            to_emails=to_emails,
            subject=Subject('Hi -name-'),
            plain_text_content=PlainTextContent(
                'Hello -name-, your URL is -github-, email sent at -time-'),
            html_content=HtmlContent(
                '<strong>Hello -name-, your URL is <a href="\&quot;-github-\&quot;">here</a></strong> email sent at -time-'),
            global_substitutions=global_substitutions,
            is_multiple=True)

        self.assertEqual(
            message.get(),
            json.loads(r'''{
                "content": [

message.bcc = [
            Bcc('test17@example.com', 'Example User17', p=1),
            Bcc('test18@example.com', 'Example User18', p=1)
        ]

        message.header = Header('X-Test5', 'Test5', p=1)
        message.header = Header('X-Test6', 'Test6', p=1)
        message.header = [
            Header('X-Test7', 'Test7', p=1),
            Header('X-Test8', 'Test8', p=1)
        ]

        message.substitution = Substitution('%name3%', 'Example Name 3', p=1)
        message.substitution = Substitution('%city3%', 'Example City 3', p=1)
        message.substitution = [
            Substitution('%name4%', 'Example Name 4', p=1),
            Substitution('%city4%', 'Example City 4', p=1)
        ]

        message.custom_arg = CustomArg('marketing3', 'true', p=1)
        message.custom_arg = CustomArg('transactional3', 'false', p=1)
        message.custom_arg = [
            CustomArg('marketing4', 'false', p=1),
            CustomArg('transactional4', 'true', p=1)
        ]

        message.send_at = SendAt(1461775052, p=1)

        message.subject = Subject('Sending with SendGrid is Fun 1', p=1)

        # The values below this comment are global to entire message

def test_unicode_values_in_substitutions_helper(self):
        from sendgrid.helpers.mail import (Mail, From, To, Subject,
                                           PlainTextContent, HtmlContent)
        self.maxDiff = None
        message = Mail(
            from_email=From('test+from@example.com', 'Example From Name'),
            to_emails=To('test+to@example.com', 'Example To Name'),
            subject=Subject('Sending with SendGrid is Fun'),
            plain_text_content=PlainTextContent(
                'and easy to do anywhere, even with Python'),
            html_content=HtmlContent(
                '<strong>and easy to do anywhere, even with Python</strong>'))
        message.substitution = Substitution('%city%', u'Αθήνα', p=1)
        self.assertEqual(
            message.get(),
            json.loads(r'''{
                "content": [

message.bcc = [ 
        Bcc('test8@example.com', 'Example User8', p=0),
        Bcc('test9@example.com', 'Example User9', p=0)
    ]

    message.subject = Subject('Sending with SendGrid is Fun 0', p=0)

    message.header = Header('X-Test1', 'Test1', p=0)
    message.header = Header('X-Test2', 'Test2', p=0)
    message.header = [
        Header('X-Test3', 'Test3', p=0),
        Header('X-Test4', 'Test4', p=0)
    ]

    message.substitution = Substitution('%name1%', 'Example Name 1', p=0)
    message.substitution = Substitution('%city1%', 'Example City 1', p=0)
    message.substitution = [
        Substitution('%name2%', 'Example Name 2', p=0),
        Substitution('%city2%', 'Example City 2', p=0)
    ]

    message.custom_arg = CustomArg('marketing1', 'true', p=0)
    message.custom_arg = CustomArg('transactional1', 'false', p=0)
    message.custom_arg = [
        CustomArg('marketing2', 'false', p=0),
        CustomArg('transactional2', 'true', p=0)
    ]

    message.send_at = SendAt(1461775051, p=0)

    message.to = To('test10@example.com', 'Example User10', p=1)
    message.to = [

message.bcc = Bcc('test7@example.com', 'Example User7', p=0)
    message.bcc = [ 
        Bcc('test8@example.com', 'Example User8', p=0),
        Bcc('test9@example.com', 'Example User9', p=0)
    ]

    message.subject = Subject('Sending with SendGrid is Fun 0', p=0)

    message.header = Header('X-Test1', 'Test1', p=0)
    message.header = Header('X-Test2', 'Test2', p=0)
    message.header = [
        Header('X-Test3', 'Test3', p=0),
        Header('X-Test4', 'Test4', p=0)
    ]

    message.substitution = Substitution('%name1%', 'Example Name 1', p=0)
    message.substitution = Substitution('%city1%', 'Example City 1', p=0)
    message.substitution = [
        Substitution('%name2%', 'Example Name 2', p=0),
        Substitution('%city2%', 'Example City 2', p=0)
    ]

    message.custom_arg = CustomArg('marketing1', 'true', p=0)
    message.custom_arg = CustomArg('transactional1', 'false', p=0)
    message.custom_arg = [
        CustomArg('marketing2', 'false', p=0),
        CustomArg('transactional2', 'true', p=0)
    ]

    message.send_at = SendAt(1461775051, p=0)

    message.to = To('test10@example.com', 'Example User10', p=1)

message.bcc = [ 
        Bcc('test17@example.com', 'Example User17', p=1),
        Bcc('test18@example.com', 'Example User18', p=1)
    ]

    message.header = Header('X-Test5', 'Test5', p=1)
    message.header = Header('X-Test6', 'Test6', p=1)
    message.header = [
        Header('X-Test7', 'Test7', p=1),
        Header('X-Test8', 'Test8', p=1)
    ]

    message.substitution = Substitution('%name3%', 'Example Name 3', p=1)
    message.substitution = Substitution('%city3%', 'Example City 3', p=1)
    message.substitution = [
        Substitution('%name4%', 'Example Name 4', p=1),
        Substitution('%city4%', 'Example City 4', p=1)
    ]

    message.custom_arg = CustomArg('marketing3', 'true', p=1)
    message.custom_arg = CustomArg('transactional3', 'false', p=1)
    message.custom_arg = [
        CustomArg('marketing4', 'false', p=1),
        CustomArg('transactional4', 'true', p=1)
    ]

    message.send_at = SendAt(1461775052, p=1)

    message.subject = Subject('Sending with SendGrid is Fun 1', p=1)

    # The values below this comment are global to entire message

]

    message.subject = Subject('Sending with SendGrid is Fun 0', p=0)

    message.header = Header('X-Test1', 'Test1', p=0)
    message.header = Header('X-Test2', 'Test2', p=0)
    message.header = [
        Header('X-Test3', 'Test3', p=0),
        Header('X-Test4', 'Test4', p=0)
    ]

    message.substitution = Substitution('%name1%', 'Example Name 1', p=0)
    message.substitution = Substitution('%city1%', 'Example City 1', p=0)
    message.substitution = [
        Substitution('%name2%', 'Example Name 2', p=0),
        Substitution('%city2%', 'Example City 2', p=0)
    ]

    message.custom_arg = CustomArg('marketing1', 'true', p=0)
    message.custom_arg = CustomArg('transactional1', 'false', p=0)
    message.custom_arg = [
        CustomArg('marketing2', 'false', p=0),
        CustomArg('transactional2', 'true', p=0)
    ]

    message.send_at = SendAt(1461775051, p=0)

    message.to = To('test10@example.com', 'Example User10', p=1)
    message.to = [ 
        To('test11@example.com', 'Example User11', p=1),
        To('test12@example.com', 'Example User12', p=1)
    ]

mail.add_content(Content("text/plain", ' '))
            mail.add_content(Content("text/html", email.body))

        if hasattr(email, 'categories'):
            for c in email.categories:
                mail.add_category(Category(c))

        if hasattr(email, 'custom_args'):
            for k, v in email.custom_args.items():
                mail.add_custom_arg(CustomArg(k, v))

        if hasattr(email, 'template_id'):
            mail.set_template_id(email.template_id)
            if hasattr(email, 'substitutions'):
                for key, value in email.substitutions.items():
                    personalization.add_substitution(Substitution(key, value))

        # SendGrid does not support adding Reply-To as an extra
        # header, so it needs to be manually removed if it exists.
        reply_to_string = ""
        for key, value in email.extra_headers.items():
            if key.lower() == "reply-to":
                reply_to_string = value
            else:
                mail.add_header({key: value})
        # Note that if you set a "Reply-To" header *and* the reply_to
        # attribute, the header's value will be used.
        if not mail.reply_to and hasattr(email, "reply_to") and email.reply_to:
            # SendGrid only supports setting Reply-To to a single address.
            # See https://github.com/sendgrid/sendgrid-csharp/issues/339.
            reply_to_string = email.reply_to[0]
        # Determine whether reply_to contains a name and email address, or

for k, v in msg.custom_args.items():
                personalization.add_custom_arg(CustomArg(k, v))

        personalization.subject = msg.subject

        for k, v in msg.extra_headers.items():
            if k.lower() == "reply-to":
                mail.reply_to = Email(v)
            else:
                personalization.add_header(Header(k, v))

        if hasattr(msg, "template_id"):
            mail.template_id = msg.template_id
            if hasattr(msg, "substitutions"):
                for k, v in msg.substitutions.items():
                    personalization.add_substitution(Substitution(k, v))
            if hasattr(msg, "dynamic_template_data"):
                personalization.dynamic_template_data = msg.dynamic_template_data

        if hasattr(msg, "ip_pool_name"):
            if not isinstance(msg.ip_pool_name, basestring):
                raise ValueError(
                    "ip_pool_name must be a {}, got: {}; ".format(
                        type(msg.ip_pool_name)))

            # Validate ip_pool_name length before attempting to add
            if not 2 <= len(msg.ip_pool_name) <= 64:
                raise ValueError(
                    "the number of characters of ip_pool_name must be min 2 and max 64, got: {}; "
                    "see https://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/"
                    "index.html#-Request-Body-Parameters".format(
                        len(msg.ip_pool_name)))