human
What is a the Python code you requested given the following:
Complete the below
def TR2(rv):

    ''''Replace tan and cot with sin/cos and cos/sin
    Examples
    >>> from sympy.simplify.fu import TR2
    >>> from sympy.abc import x
    >>> from sympy import tan, cot, sin, cos
    >>> TR2(tan(x))
    sin(x)/cos(x)
    >>> TR2(cot(x))
    cos(x)/sin(x)
    >>> TR2(tan(tan(x) - sin(x)/cos(x)))
    0'
    '''
assistant
#Here is the Python code you requested.
    def f(rv):
        if (rv.func is tan):
            a = rv.args[0]
            return (sin(a) / cos(a))
        elif (rv.func is cot):
            a = rv.args[0]
            return (cos(a) / sin(a))
        return rv
    return bottom_up(rv, f)