PERF: eliminate repeated get_option imports in period.pyx

Author: qwhelan

pandas/_libs/tslibs/parsing.pyx

@@ -47,6 +47,15 @@ cdef set _not_datelike_strings = {'a', 'A', 'm', 'M', 'p', 'P', 't', 'T'}
 
 # ----------------------------------------------------------------------
 
+_get_option = None
+
+def get_option(param):
+     global _get_option
+     if _get_option is None:
+          from pandas.core.config import get_option
+          _get_option = get_option
+     return _get_option(param)
+
 
 def parse_datetime_string(date_string, freq=None, dayfirst=False,
                           yearfirst=False, **kwargs):
@@ -117,7 +126,6 @@ def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
         freq = freq.rule_code
 
     if dayfirst is None or yearfirst is None:
-        from pandas.core.config import get_option
         if dayfirst is None:
             dayfirst = get_option("display.date_dayfirst")
         if yearfirst is None: