Investigating the get_likelihood method

[fealho]

The get_likelihood method below may not work as expected:

Copulas/copulas/multivariate/vine.py

Lines 246 to 258 in dfe3bb9

	def get_likelihood(self, uni_matrix):
	"""Compute likelihood of the vine."""
	# TODO: explain what this is supposed to do and make it work
	# TODO: Alternatively, remove it.
	num_tree = len(self.trees)
	values = np.empty([1, num_tree])
	for i in range(num_tree):
	value, new_uni_matrix = self.trees[i].get_likelihood(uni_matrix)
	uni_matrix = new_uni_matrix
	values[0, i] = value
	return np.sum(values)

An explanation of what this method does should be added, and we should investigate whether it works as expected.