def snake_to_camel( s, separator='_' ):
    """
    Converts snake to camel case

    >>> snake_to_camel('')
    ''

    >>> snake_to_camel('_x____yz')
    'XYz'

    >>> snake_to_camel('camel_case')
    'CamelCase'

    >>> snake_to_camel('r2_d2')
    'R2D2'

    >>> snake_to_camel('m1.small', '.')
    'M1Small'
    """
    return ''.join( [ w.capitalize( ) for w in s.split( separator ) ] )