docs: def look_source(self, sourcepath, library_paths=None):
          """
          Open a SCSS file (sourcepath) and find all involved file through
          imports.
  
          This will fill internal buffers ``_CHILDREN_MAP`` and ``_PARENTS_MAP``.
  
          Args:
              sourcepath (str): Source file path to start searching for imports.
  
          Keyword Arguments:
              library_paths (list): List of directory paths for libraries to
                  resolve paths if resolving fails on the base source path.
                  Default to None.
          """
          # Don't inspect again source that has allready be inspected as a
          # children of a previous source
          if sourcepath not in self._CHILDREN_MAP:
              with io.open(sourcepath, 'r', encoding='utf-8') as fp:
                  finded_paths = self.parse(fp.read())
  
              children = self.resolve(sourcepath, finded_paths,
                                      library_paths=library_paths)
  
              # Those files that are imported by the sourcepath
              self._CHILDREN_MAP[sourcepath] = children
  
              # Those files that import the sourcepath
              for p in children:
                  self._PARENTS_MAP[p].add(sourcepath)
  
              # Start recursive finding through each resolved path that has not
              # been collected yet
              for path in children:
                  if path not in self._CHILDREN_MAP:
                      self.look_source(path, library_paths=library_paths)
  
          return