docstr: Create square identity matrix n x n.
docstr_tok: ["Create","square","identity","matrix","n","x","n","."]
code: def eye(ctx, n, **kwargs):
      """
      Create square identity matrix n x n.
      """
      A = ctx.matrix(n, **kwargs)
      for i in xrange(n):
          A[i, i] = 1
      return A
  
imports: from ..libmp.backend import xrange
  import warnings
label_desc: Use image node_id 2 for calling the MatrixMethods obj's underlying member method code with example usage: obj.eye(ctx, n) and returns: A