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Link - class to represent link
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CONSTRUCTOR:
Link() - generic constructor, creates a Link with zero coordinates
Link(Link) - copy constructor
Link(index1, index2) - creates a Link between nodes index1 and index2
ATTRIBUTES:
parent (read-only) - Link's parent object, Glyph
node1, node2 (integer) - indexes of the nodes that are linked
OPERATIONS:
METHODS
ToHint() - transforms link to Hint (and returns it as a result) using parent as a source of node coordinates. Parent must exist