Feature to get descriptions from other sources when UMLS vocabulary returns None

[RyanDsilva]

There is a gap in the current implementation where for some complex entities, UMLS lookup returns description as None
Example:

text = "Spinal and bulbar muscular atrophy (SBMA) is an inherited motor neuron disease caused by the expansion of a polyglutamine tract within the androgen receptor (AR). SBMA can be caused by this easily."
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spinal  -  Spinal
Of or relating to the spine or spinal cord. 

Bulbo-Spinal Atrophy, X-Linked  -  Bulbo-Spinal Atrophy, X-Linked [Disease/Finding]
An X-linked recessive form of spinal muscular atrophy. It is due to a mutation of the gene encoding the ANDROGEN RECEPTOR. 

**Atrophy, Muscular, Spinobulbar  -  Spinobulbar atrophy (disorder)
None** 

Hereditary  -  Heritable
Transmitted from parent to child by information contained in the genes. 
..
..
..
cell growth  -  cellular growth
The process in which a cell irreversibly increases in size over time by accretion and biosynthetic production of matter similar to that already present. [GOC:ai] 

Polyglutamic Acid  -  Polyglutamic Acid [Chemical/Ingredient]
A peptide that is a homopolymer of glutamic acid. 

Androgen Receptor  -  Receptors, Androgen [Chemical/Ingredient]
Proteins, generally found in the CYTOPLASM, that specifically bind ANDROGENS and mediate their cellular actions. The complex of the androgen and receptor migrates to the CELL NUCLEUS where it induces transcription of specific segments of DNA. 

Androgen Receptor  -  Receptors, Androgen [Chemical/Ingredient]
Proteins, generally found in the CYTOPLASM, that specifically bind ANDROGENS and mediate their cellular actions. The complex of the androgen and receptor migrates to the CELL NUCLEUS where it induces transcription of specific segments of DNA. 

**Atrophy, Muscular, Spinobulbar  -  Spinobulbar atrophy (disorder)
None** 

Bonus:

• Handle duplicate entities