':param quantity: float representation of a quantity that is positive or zero
:param wallet_id: Identifier of the wallet type of this price
:type quantity: float
:type wallet_id: str
:raises ValueError: Thrown when one of the arguments are invalid'

def __init__(self, quantity, wallet_id):

    super(Quantity, self).__init__()
    if (not isinstance(quantity, (int, float))):
        raise ValueError('Quantity    must    be    an    int    or    a    float')
    if (quantity < 0):
        raise ValueError(('Quantity    must    be    positive    or    zero,    not    %f' % quantity))
    if (not isinstance(wallet_id, str)):
        raise ValueError('Wallet    id    must    be    a    string')
    self._quantity = quantity
    self._wallet_id = wallet_id
