code: def create_dependency(self, _from, to, function, comment=None):
          
          new_dependency = Cdependency()
          new_dependency.set_from(_from)
          new_dependency.set_to(to)
          new_dependency.set_function(function)
          if comment:
              new_dependency.set_comment(comment)
          self.add_dependency(new_dependency)
          return new_dependency
docs: Create a new dependency object and add it to the dependency layer
          @type _from: string
          @param _from: term id of the child node
          @type _to: string
          @param _to: term id of the parent node
          @type function: string
          @param function: grammatical function (relation) between parent and child
          @type comment: string
          @param comment: optional comment to be included