def METHOD_NAME(client_headers, request_headers):
    """Merges client_headers and request_headers into a single dictionary. If a request_header key is also present
    in the client_headers, the request_header value will override the client_header one.
    Args:
        client_headers  : dictionary, the default client's headers.
        request_headers : dictionary, request specific headers.
    Returns:
        A dictionary containing a set of both the client_headers and the request_headers
    """
    if request_headers is not None:
        client_headers.update(request_headers.copy())
    else:
        request_headers = client_headers.copy()
    return request_headers