A population of bears consists of black bears, brown bears, and white bears.
The input is an array of two elements. 
Determine whether the offspring of the two bears will return `'black'`, `'brown'`, `'white'`, `'dark brown'`, `'grey'`, `'light brown'`, or `'unknown'`.
Elements in the the array will always be a string.
## Examples:
    bear_fur(['black', 'black'])  returns 'black'
    bear_fur(['brown', 'brown'])  returns 'brown'
    bear_fur(['white', 'white'])  returns 'white'
    bear_fur(['black', 'brown'])  returns 'dark brown'
    bear_fur(['black', 'white'])  returns 'grey'
    bear_fur(['brown', 'white'])  returns 'light brown'
    bear_fur(['yellow', 'magenta'])  returns 'unknown'
def bear_fur(bears):
    bears = "".join(bears)
    dict = {
        'blackblack' : 'black',
        'brownbrown' : 'brown',
        'whitewhite' : 'white',
        'brownblack' : 'dark brown',
        'blackbrown' : 'dark brown',
        'blackwhite' : 'grey',
        'whiteblack' : 'grey',
        'brownwhite' : 'light brown',
        'whitebrown' : 'light brown'
    }
    return dict.get(bears, 'unknown')
def bear_fur(bears):
    bears = "".join(bears)
    dict = {
        'blackblack' : 'black',
        'brownbrown' : 'brown',
        'whitewhite' : 'white',
        'brownblack' : 'dark brown',
        'blackbrown' : 'dark brown',
        'blackwhite' : 'grey',
        'whiteblack' : 'grey',
        'brownwhite' : 'light brown',
        'whitebrown' : 'light brown'
    }
    return dict.get(bears, 'unknown')