@staticmethod
def head(_b, _x):
    """Determine the number of leading b's in vector x.

        Parameters
        ----------
        b: int
            Integer for counting at head of vector.
        x: array
            Vector of integers.

        Returns
        -------
        head: int
            Number of leading b's in x.
        """
    _head = 0
    for i in _x:
        if i == _b:
            _head += 1
        else:
            break
    return _head
