Module BaseTree

Match a node by specified attribute values.

``terminal`` is a special case: True restricts the search to external (leaf)
nodes, False restricts to internal nodes, and None allows all tree elements
to be searched, including phyloXML annotations.

Otherwise, for a tree element to match the specification (i.e. for the
function produced by `_attribute_matcher` to return True when given a tree
element), it must have each of the attributes specified by the keys and
match each of the corresponding values -- think 'and', not 'or', for
multiple keys.

Retrieve a matcher function by passing an arbitrary object.

i.e. passing a `TreeElement` such as a `Clade` or `Tree` instance returns an
identity matcher, passing a type such as the `PhyloXML.Taxonomy` class
returns a class matcher, and passing a dictionary returns an attribute
matcher.

The resulting 'match' function returns True when given an object matching
the specification (identity, type or attribute values), otherwise False.
This is useful for writing functions that search the tree, and probably
shouldn't be used directly by the end user.

Merge target specifications with keyword arguments.

Dispatch the components to the various matcher functions, then merge into a
single boolean function.

Convert ``[targets]`` or ``*targets`` arguments to a single iterable.

This helps other functions work like the built-in functions `max` and
`min`.