def fhir_version_name(fhir_version):
    """
    Get the name of a particular FHIR version number

    :param: fhir_version
    :type: str

    :returns: str
    """
    major_version = int(fhir_version.split(".")[0])

    if major_version < 3:
        return "dstu2"
    elif (major_version >= 3) and (major_version < 4):
        return "stu3"
    elif (major_version >= 4) and (major_version < 5):
        return "r4"
    else:
        raise Exception(
            f"Invalid fhir version supplied: {fhir_version}! No name exists "
            "for the supplied fhir version."
        )