Remove unused functions. (#598)

* Remove unused _get_branches function.

* Remove unused _flatten function.

* Define error message in one line.

signac/contrib/collection.py

@@ -59,26 +59,6 @@
 MAX_DEFAULT_ID = int("F" * 32, 16)
 
 
-def _flatten(container):
-    """Yield elements from the container.
-
-    Parameters
-    ----------
-    container : sequence
-        List or tuple of elements.
-
-    Yields
-    ------
-    Elements of container, recursively flattening sub-sequences.
-
-    """
-    for i in container:
-        if isinstance(i, (list, tuple)):
-            yield from _flatten(i)
-        else:
-            yield i
-
-
 class _DictPlaceholder:
     pass
 
@@ -304,8 +284,10 @@ def op(value, argument):
             elif len(argument) == 3:
                 argument, rel_tol, abs_tol = argument
             else:
-                err_msg = "The argument of the $near operator must be a float "
-                err_msg += "or a list of floats with length 1, 2, or 3."
+                err_msg = (
+                    "The argument of the $near operator must be a float or a list of floats with "
+                    "length 1, 2, or 3."
+                )
                 raise ValueError(err_msg)
         argument = float(argument)
         rel_tol = float(rel_tol)

signac/contrib/linked_view.py

@@ -297,35 +297,6 @@ def _build_tree(paths):
     return root
 
 
-def _get_branches(root, branch=None):
-    """Get all branches from the root node.
-
-    Parameters
-    ----------
-    root : :class:`~signac.contrib.linked_view._Node`
-        Root node.
-    branch : list
-        The current list of branches that has been collected,
-        used in recursive calls to build up the branches starting
-        at the root (Default value = None).
-
-    Yields
-    ------
-    list
-        Branches for the root node.
-
-    """
-    if branch is None:
-        branch = []
-    else:
-        branch = list(branch) + [root]
-    if root.children:
-        for child in root.children.values():
-            yield from _get_branches(child, branch)
-    else:
-        yield branch
-
-
 def _color_path(root, path):
     """Color the path from root by setting value to True.