@Nullable
  private PyAstExpression findAssignedValueInternal() {
    final PyAstAssignmentStatement assignment = PsiTreeUtil.getParentOfType(this, PyAstAssignmentStatement.class);
    if (assignment != null) {
      var mapping = assignment.getTargetsToValuesMapping();
      for (final var pair : mapping) {
        PyAstExpression assigned_to = pair.getFirst();
        if (assigned_to == this) {
          return pair.getSecond();
        }
      }
    }
    final PyAstImportElement importElement = PsiTreeUtil.getParentOfType(this, PyAstImportElement.class);
    if (importElement != null) {
      return importElement.getImportReferenceExpression();
    }
    final PyAstAssignmentExpression assignmentExpression = ObjectUtils.tryCast(getParent(), PyAstAssignmentExpression.class);
    if (assignmentExpression != null) {
      return assignmentExpression.getAssignedValue();
    }
    return null;
  }
@Nullable
  private PyAstExpression findAssignedValueInternal()