Unable to Trigger Lambda function in AWS using Python code from my local setup

I am trying to trigger a Lambda function using Python code as follows:

import boto3
from botocore.exceptions import NoCredentialsError, PartialCredentialsError

def get_lambda_client():
    return boto3.client('lambda')

def invoke_lambda():
    lambda_client = get_lambda_client()
    if lambda_client:
       try:
           response = lambda_client.invoke(
               FunctionName='MyLambdaFunctionName',
               InvocationType='RequestResponse',  # or 'event for async invocation'
               Payload=b'{}' #Not sending any payload
           )
           print(f" the response from the aws = {response}")
       except Exception as e:
           print(f" Error invoking Lambda function: {e}")

invoke_lambda()

I am using the following policies attached to the Role:

1. Policy to trigger the Lambda function:

    {
      "Version": "2012-10-17",
      "Statement": [
        {
            "Effect": "Allow",
            "Action": "lambda:InvokeFunction",
            "Resource": "< arn of my lambda function>"
        },
        {
            "Effect": "Allow",
            "Action": "sts:AssumeRole",
            "Resource": "< arn of the role I created for lambda function which intern 
             will trigger aws step function>"
      }
     ]
   }
   

2. Trusted policy for the role I created for this Lambda function trigger:

       {
         "Version": "2012-10-17",
         "Statement": [
            {
             "Effect": "Allow",
             "Principal": {
                 "Service": "lambda.amazonaws.com",
                 "AWS": "<arn for the iam user>"
                 },
             "Action": "sts:AssumeRole"
            }
          ]
        }
   

Please let me know if anything is missing here. The error I am getting when I try to trigger a lambda function from python code is:

Error invoking Lambda function: An error occurred (ExpiredTokenException) when calling the Invoke operation: The security token included in the request is expired

Suggest a solution which can be used here by assuming the sts role, considering that I don't have permission to fetch AccessKey, SecreteKey and SessionToken.

The process should work as follows:

• Your Python code will need to use AWS credentials to invoke the AWS Lambda function.
  • If you are running the Python code from an Amazon EC2 instance, then it will use credentials from the IAM Role assigned to the Amazon EC2 instance
  • If you are running the Python code from your own computer, then it will use IAM User credentials stored in the local ~/.aws/credentials configuration file (which is typically created using the aws configure command in the AWS CLI)
• The Lambda function will then automatically assume an IAM Role that has been assigned to the Lambda function. Note that this is a different IAM Role to the one that you might be using to invoke the function.

Your 'policy to trigger Lambda function' does NOT require permission to AssumeRole. It simply needs permission to invoke the Lambda function.