Aliases: wk_flatten wk_flatten_filter
Keywords:
### ** Examples wk_flatten(wkt("MULTIPOINT (1 1, 2 2, 3 3)"))
<wk_wkt[3]> [1] POINT (1 1) POINT (2 2) POINT (3 3)
wk_flatten( wkt("GEOMETRYCOLLECTION (GEOMETRYCOLLECTION (GEOMETRYCOLLECTION (POINT (0 1))))"), max_depth = 2 )
<wk_wkt[1]> [1] GEOMETRYCOLLECTION (POINT (0 1))