def checkIngredient(self, statement):
    """Checks to see if <statement> contains a valid ingredient.

    >>> self.ingredients = {"curry":("wet", 40), "bacon":("dry", None)}
    {"curry":("wet", 40), "bacon":("dry", None)}
    >>> self.checkIngredient("Put the curry into the mixing bowl")
    "curry"
    >>> self.checkIngredient("Put the bacon into the mixing bowl")
    None
    >>> self.checkIngredient("Put the poop into the mixing bowl")
    (Raises exception)
    """
    pass