Optimize symbols calls

[timkpaine]

#69

[codecov-io]

Codecov Report

Merging #70 into master will not change coverage.
The diff coverage is 94.44%.

@@           Coverage Diff           @@
##           master      #70   +/-   ##
=======================================
  Coverage   83.54%   83.54%           
=======================================
  Files          12       12           
  Lines        1264     1264           
=======================================
  Hits         1056     1056           
  Misses        208      208

Impacted Files	Coverage Δ
pyEX/refdata.py	93.33% <94.44%> (ø)	⬆️

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