import requests


def retrieve_paper(PMCID):
    """For a given PMCID,
    retrieve the papaer from Europe PMC. 
    Decoded plain text content will be returned."""
    
    URL = f"https://www.ebi.ac.uk/europepmc/webservices/rest/{PMCID}/fullTextXML"
    response = requests.get(URL)
    data = response.content.decode()
    return data