Generates the header part for shared variables

    :param name: param name
    :param doc: param doc

def _gen_param_header(name, doc, defaultValueStr, typeConverter):
    """
    Generates the header part for shared variables

    :param name: param name
    :param doc: param doc
    """
    template = '''class Has$Name(Params):
    """
    Mixin for param $name: $doc
    """

    $name = Param(Params._dummy(), "$name", "$doc", typeConverter=$typeConverter)

    def __init__(self):
        super(Has$Name, self).__init__()'''

    if defaultValueStr is not None:
        template += '''
        self._setDefault($name=$defaultValueStr)'''

    Name = name[0].upper() + name[1:]
    if typeConverter is None:
        typeConverter = str(None)
    return template \
        .replace("$name", name) \
        .replace("$Name", Name) \
        .replace("$doc", doc) \
        .replace("$defaultValueStr", str(defaultValueStr)) \
        .replace("$typeConverter", typeConverter)