docstr: Return the i-th n-dimensional unit vector.
docstr_tok: ["Return","the","i-th","n-dimensional","unit","vector","."]
code: def unitvector(ctx, n, i):
      """
      Return the i-th n-dimensional unit vector.
      """
      assert 0 < i <= n, "this unit vector does not exist"
      return [ctx.zero] * (i - 1) + [ctx.one] + [ctx.zero] * (n - i)
  
imports: from copy import copy
  from ..libmp.backend import xrange
label_desc: Use image node_id 7 for calling the LinearAlgebraMethods obj's underlying member method code with example usage: obj.unitvector(ctx, n, i) and returns: unknown