### 26.15.16 Checking whether lines form a bundle

The is_harmonic_line_bundle command determines how lines are related.

- is_harmonic_line_bundle takes L, a list or sequence of lines.
- is_harmonic_line_bundle(L) returns 1 if the lines pass through a common point. 2 if the lines are parallel, 3 if the lines are the same, and 0 otherwise.

#### Example

is_harmonic_line_bundle([line(0,1+i),line(0,2+i),line(0,3+i),line(0,1)])

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