Fix a small bug + add 2 convenience functions

[stelmo]

These 2 convenience functions will get changed with #700, but for now it is useful :)

[codecov[bot]]

Codecov Report

Base: 89.83% // Head: 89.73% // Decreases project coverage by -0.09% :warning:

Coverage data is based on head (6592b2c) compared to base (05602d3). Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## next #712 +/- ## ========================================== - Coverage 89.83% 89.73% -0.10% ========================================== Files 84 85 +1 Lines 1957 1959 +2 ========================================== Hits 1758 1758 - Misses 199 201 +2 ``` | [Impacted Files](https://codecov.io/gh/LCSB-BioCore/COBREXA.jl/pull/712?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LCSB-BioCore) | Coverage Δ | | |---|---|---| | [src/types/misc/BalancedGrowthCommunityModel.jl](https://codecov.io/gh/LCSB-BioCore/COBREXA.jl/pull/712/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LCSB-BioCore#diff-c3JjL3R5cGVzL21pc2MvQmFsYW5jZWRHcm93dGhDb21tdW5pdHlNb2RlbC5qbA==) | `100.00% <ø> (ø)` | | | [src/utils/BalancedGrowthCommunityModel.jl](https://codecov.io/gh/LCSB-BioCore/COBREXA.jl/pull/712/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LCSB-BioCore#diff-c3JjL3V0aWxzL0JhbGFuY2VkR3Jvd3RoQ29tbXVuaXR5TW9kZWwuamw=) | `0.00% <0.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LCSB-BioCore). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LCSB-BioCore)

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[stelmo]

/format

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