code: def sign(ctx, x):
      x = ctx.convert(x)
      if not x or ctx.isnan(x):
          return x
      if ctx._is_real_type(x):
          if x > 0:
              return ctx.one
          else:
              return -ctx.one
      return x / abs(x)
  
imports: from ..libmp.backend import xrange
  import math
  import cmath
label_desc: Use image node_id 16 for calling a global function with example usage: sign(ctx, x) and returns: unknown, x, ctx, unknown