Returning invalid document while ingesting data into MongoDBAtlas

Below's the code which i used to get the documents

import pandas as pd
import glob
import os
import json

class CustomCSVLoader:
    def __init__(self, file_path, metadata_columns, encoding="utf-8"):
        self.file_path = file_path
        self.metadata_columns = metadata_columns
        self.encoding = encoding

    def load(self):
        # Load the CSV file with the specified encoding
        df = pd.read_csv(self.file_path, encoding=self.encoding)
        # Filter the dataframe based on the specified metadata columns and add any additional columns if needed
        if self.metadata_columns:
            df = df[self.metadata_columns + ['Text']]
        # Convert the dataframe to a dictionary, then to the desired format
        my_dict = json.loads(df.to_json(orient='index'))
        documents = self._process_chunks(my_dict)
        return documents

    def _process_chunks(self, my_dict):
        chunks = [item for item in my_dict.values()]
        for chunk in chunks:
            # Assuming get_token_set is a function you've defined elsewhere
            chunk.update({'token_set': get_token_set(chunk['Text'])})
        # Assuming Document is a class you've defined elsewhere and removekey is a function to remove keys from a dict
        docs = [Document(page_content=item['Text'], metadata=removekey(item, 'Text')) for item in chunks]
        return docs

def load_csv_files(folder_path):
    csv_files = glob.glob(os.path.join(folder_path, '*.csv'))
    metadata_columns = ['x1', 'y1', 'x2', 'y2', 'page_no', 'source_url', 'doc_type', 'company', 'doc_year']
    documents = []
    for file_path in csv_files:
        loader = CustomCSVLoader(file_path=file_path, metadata_columns=metadata_columns)
    return documents

folder_path = 'data'  
docs= load_csv_files(folder_path)


below’s the output of the docs[0]

Document(page_content='what's happening over there.', metadata={'x1': 198.7965924442, 'y1': 204.7538135126, 'x2': 1448.4322473817, 'y2': 1536.8232888756, 'page_no': 1, 'source_url': 'data.pdf', 'doc_type': 'sports', 'company': 'BCCI', 'doc_year': 2022, 'token_set': {'publicly', 'the', 'that'}})

then i wrote a code which will ingest the above data into MongoDBAtlas

db = MongoDBAtlasVectorSearch.from_documents(

and below is the output

InvalidDocument: cannot encode object: {{'publicly', 'the', 'that'}})

I successfully imported data into MongoDB Atlas using the CSVLoader from Langchain. However, when I attempted to modify the data by adding custom values and import it again without using CSVLoader, I encountered issues. This happened despite maintaining the same data format. I am looking for guidance on how to import data with custom modifications into MongoDB Atlas without using CSVLoader.