class_docstr: Polar transform
  
  Maps (theta, r, z) to (x, y, z), where `x = r*cos(theta)`
  and `y = r*sin(theta)`.
class_docstr_tok: ["Polar","transform","Maps","(","theta",",","r",",","z",")","to","(","x",",","y",",","z",")",",","where","`","x","=","r","*","cos","(","theta",")","`","and","`","y","=","r","*","sin","(","theta",")","`","."]
code: def map(self, coords):
      ret = np.empty(coords.shape, coords.dtype)
      ret[..., 0] = coords[..., 1] * np.cos(coords[..., 0])
      ret[..., 1] = coords[..., 1] * np.sin(coords[..., 0])
      for i in range(2, coords.shape[-1]):  # copy any further axes
          ret[..., i] = coords[..., i]
      return ret
  
imports: from __future__ import division
  import numpy
  from ._util import arg_to_array, arg_to_vec4, as_vec4
  from .base_transform import BaseTransform
  from ...None import gloo
label_desc: Use image node_id 1 for calling the PolarTransform obj's underlying member method code with example usage: obj.map(coords) and returns: ret