tagged_nodes: Generate URLs for specifically tagged nodes on a neuron
In fmlove/tracerutils: Utilities for EM Neuron Tracers

Given a neuron and a particular tag, this will return a data frame (optionally written to a CSV) with the node IDs, coordinates, and CATMAID URLs.

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tagged_nodes(neuron = NULL, tag, node.id = NULL,
  node.direction = c("downstream", "upstream"), volume = NULL,
  fileout = NULL)

`neuron`	Required; a A CATMAID `neuron` object or skeleton ID.
`tag`	Required; a string specifying a tag.
`node.id`	Optional; the ID of a node at which to cut the neuron, if only a portion of the neuron should be considered.
`node.direction`	If a cut node is provided, which portion of the cut neuron to retain. Options are `downstream` (default) or `upstream`.
`volume`	Optional; a string specifying a FAFB neuropil to filter the tagged nodes.
`fileout`	Optional; the path to a CSV file where the result should be written.