'Set the dissimilarity (distance) matrix.
Parameters
matrix : Optional[Orange.misc.DistMatrix]'

@Inputs.distances
def set_disimilarity(self, matrix):

    if ((matrix is not None) and (len(matrix) < 2)):
        self.Error.matrix_too_small()
        matrix = None
    else:
        self.Error.matrix_too_small.clear()
    self.matrix = matrix
    if ((matrix is not None) and matrix.row_items):
        self.matrix_data = matrix.row_items
    if (matrix is None):
        self.matrix_data = None
    self._invalidated = True
    self._selection_mask = None
