The C Transformers library provides Python bindings for GGML models. This example goes over how to use LangChain to interact with C Transformers models. Install 
%pip install -qU  ctransformers
Load Model 
from langchain_community.llms import CTransformers

llm = CTransformers(model="marella/gpt-2-ggml")
Generate Text 
print(llm.invoke("AI is going to"))
Streaming 
from langchain_core.callbacks import StreamingStdOutCallbackHandler

llm = CTransformers(
    model="marella/gpt-2-ggml", callbacks=[StreamingStdOutCallbackHandler()]
)

response = llm.invoke("AI is going to")
LLMChain 
from langchain.chains import LLMChain
from langchain_core.prompts import PromptTemplate

template = """Question: {question}

Answer:"""

prompt = PromptTemplate.from_template(template)

llm_chain = LLMChain(prompt=prompt, llm=llm)

response = llm_chain.run("What is AI?")