input: Write a python function to search for documents in an Elasticsearch index using a specified query term.
  assert search_documents("index_name", "query_term") != []
  assert type(search_documents("index_name", "another_query_term")) == list
  assert len(search_documents("index_name", "non_existent_term")) == 0
output: def search_documents(index_name, query_term):
      from elasticsearch import Elasticsearch
      
      es = Elasticsearch()
  
      query = {
          "query": {
              "match": {
                  "content": query_term
              }
          }
      }
  
      response = es.search(index=index_name, body=query)
  
      return [hit['_source'] for hit in response['hits']['hits']]