old_contents: import os
  from xml.etree.ElementInclude import include
  import yaml
  
  
  class Content(yaml.YAMLObject):
    yaml_tag = u'!Content'
    yaml_loader = yaml.SafeLoader
  
    data = None
  
    def __init__(self, path=None, data=None):
      self.path = path
      self.data = data
  
  
  class Laul(yaml.YAMLObject):
    yaml_tag = u'!Laul'
    yaml_loader = yaml.SafeLoader
  
    def __init__(
            self,
            title=None,
            composer=None,
            poet=None,
            margin=None,
            index=None,
            misc=None,
            paths=None):
      self.title = title
      self.composer = composer
      self.poet = poet
      self.margin = margin
      self.index = index
      self.misc = misc
      self.paths = paths
      self.verses = None
      self.music = None
      self.image = None
  
    def poet_or_composer(self):
      return self.poet != None or self.composer != None
  
  
  class Project(yaml.YAMLObject):
    yaml_tag = u'!Project'
    yaml_loader = yaml.SafeLoader
  
    def __init__(self, title, subtitle, parts):
      self.title = title
      self.subtitle = subtitle
      self.parts = parts
      self.content = None
  
  
  class ProjectMeta(object):
    def __init__(
            self,
            key,
            project,
            paths):
      self.key = key
      self.project = project
      self.paths = paths
      self.__version = False
  
    @property
    def version(self):
      if self.__version is False:
        if os.path.isfile(self.paths.version):
          with open(self.paths.version) as f:
            self.__version = f.read().strip()
        else:
          self.__version = None
      return self.__version
  
  
  class ProjectPaths(object):
    def __init__(
            self,
            config,
            latex=None,
            pdf=None,
            version=None):
      self.config = config
      self.latex = latex
      self.pdf = pdf
      self.version = version
  
new_contents: import os
  from xml.etree.ElementInclude import include
  import yaml
  
  
  class Content(yaml.YAMLObject):
    yaml_tag = u'!Content'
    yaml_loader = yaml.SafeLoader
  
    data = None
  
    def __init__(self, path=None, data=None):
      self.path = path
      self.data = data
  
  
  class Laul(yaml.YAMLObject):
    yaml_tag = u'!Laul'
    yaml_loader = yaml.SafeLoader
  
    def __init__(
            self,
            title=None,
            composer=None,
            poet=None,
            margin=None,
            index=None,
            misc=None,
            paths=None):
      self.title = title
      self.composer = composer
      self.poet = poet
      self.margin = margin
      self.index = index
      self.misc = misc
      self.paths = paths
      self.verses = None
      self.music = None
      self.image = None
  
    @classmethod
    def from_yaml(cls, loader, node):
      fields = loader.construct_mapping(node)
      return Laul(**fields)
  
    def poet_or_composer(self):
      return self.poet != None or self.composer != None
  
  
  class Project(yaml.YAMLObject):
    yaml_tag = u'!Project'
    yaml_loader = yaml.SafeLoader
  
    def __init__(self, title, subtitle, parts):
      self.title = title
      self.subtitle = subtitle
      self.parts = parts
      self.content = None
  
  
  class ProjectMeta(object):
    def __init__(
            self,
            key,
            project,
            paths):
      self.key = key
      self.project = project
      self.paths = paths
      self.__version = False
  
    @property
    def version(self):
      if self.__version is False:
        if os.path.isfile(self.paths.version):
          with open(self.paths.version) as f:
            self.__version = f.read().strip()
        else:
          self.__version = None
      return self.__version
  
  
  class ProjectPaths(object):
    def __init__(
            self,
            config,
            latex=None,
            pdf=None,
            version=None):
      self.config = config
      self.latex = latex
      self.pdf = pdf
      self.version = version
  
subject: Fix constructor for files with optional arguments