jinja2 no loader for this environment error?

Question

Python

Reading template from file, template directory and name are correct, template object is created.
Here is the code.

import markdown
import os
import hashlib
from jinja2 import Template
from jinja2 import Environment, FileSystemLoader
print(os.listdir("../templates"))
loader = FileSystemLoader("../templates")
print (loader)
env = Environment(loader)
template = env.get_template("post")

files = os.listdir("docs")
def isChange(item):
    if True:
        return True
    return False
def posts_create(directory,out):#,loader,template,env):
    
    for item in directory:
        filename = item[0:-3]
        with open(directory+"/"+item,"r",encoding = "utf-8") as f:
             with open (out+"/"+filename+".html","w+",encoding = "utf-8") as html:
# вывод шаблонизатора +
                data = {"header":f.readline()[2:], "content":markdown.markdown(f.read())}
                html.write(template.render(data))

posts_create(files,"../days")