'Check if ``X`` is a sample from a Multinomial distribution.
That is ``X`` should be an array of non-negative integers from
range ``[min(X), max(X)]``, such that each integer from the range
occurs in ``X`` at least once.
For example ``[0, 0, 2, 1, 3, 1, 1]`` is a valid sample from a
Multinomial distribution, while ``[0, 0, 3, 5, 10]`` is not.'

def _check_input_symbols(self, X):

    symbols = np.concatenate(X)
    if ((len(symbols) == 1) or (symbols.dtype.kind != 'i') or (symbols < 0).any()):
        return False
    symbols.sort()
    return np.all((np.diff(symbols) <= 1))
