code: def _test_color_function(self):
      if not callable(self.f):
          raise ValueError("Color function is not callable.")
      try:
          result = self.f(0, 0, 0, 0, 0)
          if len(result) != 3:
              raise ValueError("length should be equal to 3")
      except TypeError:
          raise ValueError(
              "Color function needs to accept x,y,z,u,v, "
              "as arguments even if it doesn't use all of them."
          )
      except AssertionError:
          raise ValueError(
              "Color function needs to return 3-tuple r,g,b."
          )
      except Exception:
          pass
  
imports: from sympy.core.basic import Basic
  from sympy.core.symbol import Symbol, symbols
  from sympy.utilities.lambdify import lambdify
  from .util import interpolate, rinterpolate, create_bounds, update_bounds
  from sympy.utilities.iterables import sift
label_desc: Use image node_id 6 for calling the ColorScheme obj's underlying member method code with example usage: obj._test_color_function() without return types