changed to using existing function _ensure_encoded in parsers.pyx

pandas/_libs/parsers.pyx

@@ -275,16 +275,10 @@ cdef extern from "parser/io.h":
 
 DEFAULT_CHUNKSIZE = 256 * 1024
 
-
-def c_type_conv(st):
-    cdef bytes py_bytes = st.encode()
-    return py_bytes
-
-
 # common NA values
 # no longer excluding inf representations
 # '1.#INF','-1.#INF', '1.#INF000000',
-_NA_VALUES = [c_type_conv(x) for x in parsers._NA_VALUES]
+_NA_VALUES =_ensure_encoded(in parsers._NA_VALUES)
 
 
 cdef class TextReader: