def transform_headers(
    request: requests.Request,
    prepared_request: requests.PreparedRequest
) -> None:
    """Apply various transformations on top of the `prepared_requests`'s
    headers to change the request prepreation behavior."""

    # Remove 'Content-Length' when it is misplaced by requests.
    if (
        prepared_request.method in IGNORE_CONTENT_LENGTH_METHODS
        and prepared_request.headers.get('Content-Length') == '0'
        and request.headers.get('Content-Length') != '0'
    ):
        prepared_request.headers.pop('Content-Length')

    apply_missing_repeated_headers(
        request.headers,
        prepared_request
    )
Apply various transformations on top of the `prepared_requests`'s
    headers to change the request prepreation behavior.
httpie/client.py