Not able to attach excel file to automated email using python

Question

Iam writing a function to send email with excel attachment. But I am having some issues while calling the function . I am AWS server sending the email. I have pasted my email sending function along with the function call.

Email Function

import os
from email.mime.text import MIMEText
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart

import boto3
from botocore.exceptions import ClientError

EMAIL_FROM = 'abc@gmail.com'
STAGE = os.getenv('STAGE')
ses = boto3.client('ses', 'eu-west-1')


def send(to: list, subject: str, body: str):
    try:
        ses.send_email(
            Destination={
                'ToAddresses': to
            },
            Message={
                'Body': {
                    'Text': {
                        'Charset': 'UTF-8',
                        'Data': body,
                    },
                },
                'Subject': {
                    'Charset': 'UTF-8',
                    'Data': f"[{STAGE}] {subject}",
                },
            },
            Source=EMAIL_FROM
        )
    except ClientError as e:
        raise ValueError(e.response['Error']['Message'])


def send_with_attachment(to: list, subject: str, body: str, attachments: dict):
    message = MIMEMultipart()
    message['Subject'] = f"[K+N:{STAGE}] {subject}"
    message['From'] = EMAIL_FROM
    message['To'] = ','.join(to)

    part = MIMEText(body)
    message.attach(part)

    # attachments
    for filename, content in attachments.items():
        part = MIMEApplication(str.encode(content))
        part.add_header('Content-Disposition', 'attachment', filename=filename)
        message.attach(part)

    try:
        ses.send_raw_email(
            Source=message['From'],
            Destinations=to,
            RawMessage={
                'Data': message.as_string()
            }
        )
    except ClientError as e:
        raise ValueError(e.response['Error']['Message'])

Calling Function

send_with_attachment(
        to='xyz@gmail.com',
        subject='Report',
        body='Test',
        attachments={ 
            open('Report.xlsx', 'rb')

        }

    )

 Error : 'set' object has no attribute 'items'

I am having issue while calling the function. Any help on how to resolve the issue.