message: Update api_def_Polygamma.pbtxt
diff: op {
  graph_op_name: "Polygamma"
  - summary: "Compute the polygamma function \\(\psi^{(n)}(x)\\)."
  + summary: "Compute the polygamma function \\\\(\\psi^{(n)}(x)\\\\)."
  description: <<END
  The polygamma function is defined as:
  