Saving data into solr with pysolr get rejected 'AttributeError: 'str' object has no attribute 'items''

I'm using pysolr to save a list of classes into my local solr database, my problem is that when i encode my list of classes with jsonpickle, the query is rejected with this message, although if i print the json generated by josnpickle i get no problem saving the data into solr.

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-3b6d9f42d0ec> in <module>()
     27 json=str(jsonpickle.encode(coreData, unpicklable=False))
     28 print(json)
---> 29 solr.add(json)

    C:\ProgramData\Anaconda3\lib\site-packages\pysolr.py in add(self, docs, boost, fieldUpdates, commit, softCommit, commitWithin, waitFlush, waitSearcher, overwrite, handler)
        878 
        879         for doc in docs:
    --> 880             el = self._build_doc(doc, boost=boost, fieldUpdates=fieldUpdates)
        881             message.append(el)
        882 

    C:\ProgramData\Anaconda3\lib\site-packages\pysolr.py in _build_doc(self, doc, boost, fieldUpdates)
        798         doc_elem = ElementTree.Element('doc')
        799 
    --> 800         for key, value in doc.items():
        801             if key == NESTED_DOC_KEY:
        802                 for child in value:

    AttributeError: 'str' object has no attribute 'items'

my code:

from solrq import Q
import pysolr
import jsonpickle
from datetime import datetime, timedelta
from Model import Twitter



#conexion a solr
solr = pysolr.Solr('http://localhost:8983/solr/twitter')

#query
query = Q(label="none")
results = solr.search(query)


print("Saw {0} result(s).".format(len(results)))

#testing the query
for result in results:
    print("-->".format(result['content']))

#creating a new class with data    
twit = Twitter("000002","content text","some label")  
#list of twitter classes
coreData=[]

coreData.append(twit)
#encoding to json
json=str(jsonpickle.encode(coreData, unpicklable=False))

print(json)
#saving to solr
solr.add(json)

This is what prints after encoding the list of classes into json [{"content": "content text", "id": "000002", "label": "some label"}] as i said before if i substitute the json variable with this string the data is saved but i have no idea why, even if cast as a string like this solr.add(str(json)) get the same error message.

The problem here is, that pysolr for method add

Requires docs, which is a list of dictionaries. Each key is the field name and each value is the value to index.

You need to create dictionary from your object, not strings. You could do it by calling vars on an object

coreData=[]
coreData.append(vars(twit))
solr.add(coreData)