'Initialize an annotation task.
The data argument can be None (to create an empty annotation task) or a sequence of 3-tuples,
each representing a coder\'s labeling of an item:
(coder,item,label)
The distance argument is a function taking two arguments (labels) and producing a numerical distance.
The distance from a label to itself should be zero:
distance(l,l) = 0'

def __init__(self, data=None, distance=binary_distance):

    self.distance = distance
    self.I = set()
    self.K = set()
    self.C = set()
    self.data = []
    if (data is not None):
        self.load_array(data)
