code: def _parse_extra_features(node, NHX_string):
      
      NHX_string = NHX_string.replace("[&&NHX:", "")
      NHX_string = NHX_string.replace("]", "")
      for field in NHX_string.split(":"):
          try:
              pname, pvalue = field.split("=")
          except ValueError as e:
              raise NewickError('Invalid NHX format %s' %field)
          node.add_feature(pname, pvalue)
docs: Reads node's extra data form its NHX string. NHX uses this
      format:  [&&NHX:prop1=value1:prop2=value2]