docstr: Write colors to a yaml file
code: def to_yaml(self, filename):
      """Write colors to a yaml file"""
      with open(filename, "w") as outfile:
          yaml.dump(self.colors, outfile, default_flow_style=False)
  
imports: from collections import OrderedDict
  from bokeh import palettes
  from IPython.core.display import HTML
  import yaml
  from chartify._core.options import options
  from chartify._core import colour
label_desc: Use image node_id 2 for calling the CustomColors obj's underlying member method code with example usage: obj.to_yaml(filename) without return types