Write the function `resistor_parallel` that receive an undefined number of resistances parallel resistors and return the total resistance.

You can assume that there will be no 0 as parameter.  
Also there will be at least 2 arguments.

Formula:  
`total = 1 / (1/r1 + 1/r2 + .. + 1/rn)`

Examples:  
`resistor_parallel(20, 20)` will return `10.0`  
`resistor_parallel(20, 20, 40)` will return `8.0`

Difficulty: introductory

Starter code:

def resistor_parallel(*resistors):
	

Solutions:
def resistor_parallel(*rs):
    return 1 / sum(1.0 / r for r in rs)

def resistor_parallel(*resistances):
    return 1 / sum(1.0 / r for r in resistances)

def resistor_parallel(*xs):
    return 1 / sum(1 / x for x in map(float, xs))

resistor_parallel = lambda *args: 1 / sum(1.0 / i for i in args)

def resistor_parallel(*resistors):
    return 1 / (sum(1 / resistor for resistor in resistors))


def resistor_parallel(*args):
    sum = 0
    for i in args:
      sum += 1/i
    return 1/sum


def resistor_parallel(*args):
    return 1 / sum(1.0 / a for a in args)


def resistor_parallel(*resistors):
    return 1.0 / sum(map(lambda x:1.0/x, resistors))

resistor_parallel = lambda *args: 1/sum(1./x for x in args)

from functools import reduce

def resistor_parallel(*res):
    # it take an unlimited number of arguments 
    # create the function resistor_parallel
    
    return 1 / reduce(lambda x, y: x + y, [1/x for x in res])