added IndentedTextImporter, compatible docstrings, & nose tests

[LionKimbro]

No description provided.

[coveralls]

Coverage decreased (-0.3%) to 99.43% when pulling 4db02fe on LionKimbro:master into d63289b on c0fec0de:master.

[lverweijen]

I would be interested in this.

Some features I would want:

• Make indentchar flexible. So not only space, but should also be able to use tab, "." or any other character
• Provide your own node-class to use
• Similar functionality to export to an indented tree-file (which does not write the root or this should be made an option)

Here sample implementations:

def from_indented(file, indent=' ', node_factory=anytree.Node):
    """
    node_factory receives one argument and should create a node
    indent should be "    " if exactly 4 spaces are used
    """

    # Each line consists of indent and code
    pattern = re.compile(rf"^(?P<prefix>({re.escape(indent)})*)(?P<code>.*)")

    root = node_factory()
    stack = [root]

    for line in file:
        match = pattern.match(line)
        prefix, code = match['prefix'], match['code']
        depth = len(prefix) // len(indent)
        node = node_factory(code)
        node.parent = stack[depth]

        # Place node as last item on index depth + 1
        del stack[depth + 1:]
        stack.append(node)

    return root


def to_indented(root, file, indent=" ", depth=0, formatter=str):
    """
    formatter is how the node should be displayed, maybe lambda x: x.name is also a good default
    formatter should be the inverse of node_factory in the previous function
    depth is the beginning level, normally 0 meaning no indent for first depth-level
    root is not included in the output
    """
    for child in root.children:
        file.write(indent * depth + formatter(child) + '\n')
        to_indented(child, file, indent=indent, depth=depth + 1, formatter=formatter)