make string an r-string to avoid escaping backslash

validphys2/src/validphys/arclength.py

@@ -3,6 +3,7 @@
 
 Module for the computation and presentation of arclengths.
 """
+
 from collections import namedtuple
 from collections.abc import Sequence
 import numbers
@@ -150,7 +151,7 @@ def integrability_number(
     basis: (str, Basis) = "evolution",
     flavours: (list, tuple, type(None)) = None,
 ):
-    """Return \sum_i |x_i*f(x_i)|, x_i = {1e-9, 1e-8, 1e-7}
+    r"""Return \sum_i |x_i*f(x_i)|, x_i = {1e-9, 1e-8, 1e-7}
     for selected flavours
     """
     checked = check_basis(basis, flavours)