import typing


def add_to_dict(data_dict: typing.Dict[str, str], key: str, value: str) -> None:
    """
    Add key, value pair to dictionary.
    Raise an AttributeError in case the key already exists in the dictionary.

    Arguments:
    data_dict - Dictionary that needs to be filled
    key - Key that needs to be added
    value - Value that needs to be added related to the key

    Returns:
    None
    """
    if key.strip() in data_dict:
        raise AttributeError(f'Key: {key} already exists in data_dict!')
    else:
        if isinstance(value, str):
            data_dict[key.strip()] = value.strip()
        else:
            data_dict[key.strip()] = value
    return None