Handle Sympy Builtin Symbols to Avoid Errors in Reactions #4
Description
Address the issue where the use of Sympy's builtin symbols (e.g., "S") within reaction definitions leads to errors, as seen in reactions like "S -> P; k1*S". Currently, using certain builtin symbols as part of the reaction or rate law notation triggers exceptions due to symbol conflicts. This problem necessitates a solution that either restricts the use of these specific builtin symbols in reaction definitions or implements a mechanism to distinguish between user-defined symbols and Sympy's builtin symbols. This enhancement will ensure greater flexibility and reliability in defining reactions without encountering unexpected errors.